ChatGPT answers, unedited

For an agency managing multiple ecommerce stores on a tight budget, I’d focus heavily on multi-store management, reusable templates/flows, and how SMS costs scale rather than simply picking the most powerful platform.

My shortlist

Why I'd look at Omnisend first

The particularly relevant feature for your setup is multi-store accounts. Omnisend lets you switch between stores from one account and, importantly, reuse templates and workflows across stores rather than rebuilding everything for every client. Omnisend Omnisend Help Center

Its current pricing also starts relatively low: the published pricing shows a free tier and paid plans beginning around $16/month, while SMS pricing is now usage-based and varies by country/volume. Omnisend

That makes it interesting if your agency has, say, 10–30 smaller stores where paying a full expensive marketing platform subscription for every individual client would eat your margin.

One important 2026 caveat: don't rely on old Omnisend comparisons saying SMS is included in the cheaper plans. Omnisend changed its SMS offering in May 2026; its current pricing should be used when modeling your costs. Omnisend Omnisend

When I'd use Klaviyo instead

klaviyo.com makes more sense if your clients have substantial customer lists and you need things like sophisticated behavioral segmentation, complex flows, predictive analytics, and detailed revenue attribution.

The tradeoff is that the economics become more important as the number of contacts grows. For a budget-conscious agency, I'd be cautious about putting every small client on Klaviyo simply because it's the most familiar ecommerce option.

A potentially cheaper agency stack

If your clients don't need extremely sophisticated ecommerce segmentation, I'd also investigate brevo.com. Its pricing model is oriented more toward sending volume than simply accumulating contacts, which can be attractive for agencies with lots of relatively small lists. Tajo

The compromise is that the ecommerce-specific experience isn't necessarily as deep as a dedicated platform like Klaviyo or Omnisend.

What I'd do for your agency

I'd structure it roughly like this:

• Small/medium Shopify or WooCommerce clients → Omnisend
• Higher-revenue clients with complex lifecycle marketing → Klaviyo
• Very low-volume clients → evaluate Brevo
• One standardized agency template/flow library → primarily Omnisend, because its multi-store sharing functionality directly addresses your operational overhead.

The big thing I'd calculate before committing is cost per client at 1k, 5k, 10k and 25k contacts + their monthly SMS volume. That's where the "cheap" platform can suddenly become expensive.

If you tell me roughly how many shops you manage, average contacts per shop, and monthly SMS volume, I can build a concrete agency cost comparison for Omnisend vs Klaviyo vs Brevo, including what your approximate monthly software bill would look like.

Its current pricing also starts relatively low: the published pricing shows a free tier and paid plans beginning around $16/month, while SMS pricing is now usage-based and varies by country/volume. Omnisend

That makes it interesting if your agency has, say, 10–30 smaller stores where paying a full expensive marketing platform subscription for every individual client would eat your margin.

One important 2026 caveat: don't rely on old Omnisend comparisons saying SMS is included in the cheaper plans. Omnisend changed its SMS offering in May 2026; its current pricing should be used when modeling your costs. Omnisend Omnisend

When I'd use Klaviyo instead

klaviyo.com makes more sense if your clients have substantial customer lists and you need things like sophisticated behavioral segmentation, complex flows, predictive analytics, and detailed revenue attribution.

The tradeoff is that the economics become more important as the number of contacts grows. For a budget-conscious agency, I'd be cautious about putting every small client on Klaviyo simply because it's the most familiar ecommerce option.

A potentially cheaper agency stack

If your clients don't need extremely sophisticated ecommerce segmentation, I'd also investigate brevo.com. Its pricing model is oriented more toward sending volume than simply accumulating contacts, which can be attractive for agencies with lots of relatively small lists. tajo.io

The compromise is that the ecommerce-specific experience isn't necessarily as deep as a dedicated platform like Klaviyo or Omnisend.

What I'd do for your agency

I'd structure it roughly like this:

For an agency managing multiple ecommerce stores on a tight budget, I’d shortlist these:

• omnisend.com — my first choice for your use case. It supports multiple stores under one login, lets you copy templates, workflows and segments between stores, and supports up to 500 stores under one account. Each store remains isolated for contacts, automations and reporting. Omnisend Help Center

• Current Standard pricing starts at $16/month normally (the site is currently showing a first-3-month promotional price of $11.20).
• SMS is available on the current Pro plan, with US/Canada SMS starting at $0.007/message depending on volume. Omnisend Help Center Omnisend
• Particularly attractive if your shops are Shopify/WooCommerce-style DTC stores and you want reusable ecommerce automations.
• klaviyo.com — strongest if clients need sophisticated segmentation/automation. Klaviyo supports multiple accounts under one login, which works well for agencies, but each ecommerce site generally needs its own Klaviyo account. Klaviyo Help Center

• It also has shared billing, allowing up to 20 self-serve accounts to draw from a pooled email/SMS allocation. Klaviyo Help Center
• I'd consider it when clients are large enough that advanced customer-data capabilities justify the additional cost/complexity.
• brevo.com — budget-oriented alternative. Its platform combines email, SMS, WhatsApp and CRM features. The free tier includes 300 email sends/day and up to 100,000 stored contacts; paid plans start at $9/month. Brevo Help

• The catch for ecommerce agencies is that it's less purpose-built around ecommerce flows/product data than Omnisend or Klaviyo.

What I'd do as an agency

Standardize on Omnisend, unless you have a specific client requirement for Klaviyo.

The big agency advantage isn't just the subscription price: you can build a master set of welcome, abandoned-cart, browse-abandonment, post-purchase, win-back and promotional templates, then copy them across client stores. Omnisend explicitly supports copying templates/workflows/segments between stores. Omnisend Help Center

I'd structure it roughly as:

Agency account → Client/store 1, Client/store 2, Client/store 3...

That gives you centralized access while keeping each client's customer data and reporting separated.

One important cost consideration: Omnisend bills each store separately based on its contacts, so it isn't literally one cheap subscription covering all your clients. Omnisend Help Center If you tell me roughly how many stores you manage, average contacts per store, and monthly email/SMS volume, I can work out which setup is likely to be cheapest and compare Omnisend vs Klaviyo vs Brevo for your agency.

For an agency managing multiple ecommerce stores on a tight budget, I’d shortlist these three:

My pick for an agency

I'd start with Brevo if your priority is minimizing the agency's software bill.

Its pricing structure is particularly interesting for an agency: you can have large contact databases without necessarily paying simply because those contacts exist. For example, current pricing starts at $9/month for 5,000 emails, with SMS purchased separately. Omnisend

However, there's an important caveat: Brevo becomes less attractive if you need sophisticated ecommerce automation. Its higher-tier ecommerce functionality can get expensive, at which point Omnisend or Klaviyo may make more sense. Omnisend

If you're managing Shopify stores

I'd probably choose Omnisend.

It's more purpose-built for ecommerce than Brevo, with the standard flows you'd expect—abandoned cart, welcome, post-purchase, win-back, etc.—without immediately jumping to Klaviyo-level pricing. SaaSTracker

One thing to watch in 2026: Omnisend's SMS economics have changed, so don't assume that "email + SMS" means all SMS usage is bundled into the subscription. SaaSTracker

The agency architecture I'd use

Rather than trying to put all clients into one shared customer database, I'd structure it as:

• One account/workspace per client/store — keeps customer data, consent and reporting separated.
• One agency master login/team access — so your staff can manage the accounts.
• Reusable automation templates — welcome series, abandoned cart, post-purchase, win-back, birthday, etc.
• Reusable campaign templates — Black Friday, product launch, sale, replenishment.
• Centralized SOPs — your team duplicates the same proven flows into each store.
• Client pays the platform/SMS usage, ideally directly, while you charge your management fee separately.

That gives you the operational efficiency of a shared agency system without mixing customer data between unrelated shops.

Bottom line:
Brevo = cheapest/broadest, Omnisend = best value for ecommerce, Klaviyo = best performance/features when the client can afford it. Current 2026 comparisons broadly reach the same conclusion. TechSifted maestra.io

If you tell me roughly how many stores you manage, average contacts per store, and whether they're Shopify/WooCommerce, I can work out which option would likely give your agency the lowest monthly cost.

If you're managing Shopify stores

I'd probably choose Omnisend.

It's more purpose-built for ecommerce than Brevo, with the standard flows you'd expect—abandoned cart, welcome, post-purchase, win-back, etc.—without immediately jumping to Klaviyo-level pricing.

One thing to watch in 2026: Omnisend's SMS economics have changed, so don't assume that "email + SMS" means all SMS usage is bundled into the subscription.

The agency architecture I'd use

For an agency managing multiple ecommerce shops on a tight budget, I would optimize for:

• Multi-store/client management
• Separate customer lists and sending reputations
• Team access/permissions
• Reusable templates and flows
• Reasonable per-store costs
• Email + SMS in one platform

My shortlist:

Maestra Campaign Monitor## My recommendation for your situation

Option 1: Omnisend as your agency default

This is probably where I’d start.

Why:

• Built around ecommerce use cases (abandoned cart, browse abandonment, post-purchase, winback)
• Handles email + SMS together
• Lower learning curve for junior staff
• Easier to standardize across many stores
• Good fit when clients are small-to-mid sized

Omnisend OmnisendA practical agency setup:

• One agency master account/team
• One workspace per client store
• Shared flow templates: - Welcome series
• Abandoned cart
• Browse abandonment
• Post-purchase cross-sell
• Review request
• Winback
• VIP/customer birthday

Option 2: Klaviyo only for your best clients

I would not put every small client on Klaviyo if margins are tight.

Use it when:

• Store revenue is already meaningful
• They have large customer lists
• They need advanced segmentation
• You charge a retention-management fee

Klaviyo is excellent for ecommerce lifecycle marketing, but the cost structure can become painful when you have many smaller accounts. Noctilucens

Option 3: A cheaper multi-store specialist

If you mainly manage Shopify stores and need the lowest operational cost, look at newer multi-store-focused tools such as trymailflow.com, which positions itself specifically around managing multiple Shopify stores with email/SMS in one workspace. MailFlow I’d evaluate deliverability and feature depth carefully before making it your core client platform.

What I would avoid

• Running every client through one shared subscriber database (privacy/compliance headache)
• Mixing client sending domains/reputations
• Using separate email + SMS vendors unless a client is large enough to justify it
• Building every flow from scratch

A lean agency stack I’d consider

• Small Shopify stores (<$10k/mo): Omnisend
• Growing DTC stores ($10k–$100k/mo): Omnisend → Klaviyo migration path
• Large brands: Klaviyo
• Internal reporting: Looker Studio or client dashboards
• Templates: Build 10–15 proven flows and clone/customize per store

One question would change my recommendation quite a bit: are these mostly Shopify stores, WooCommerce stores, or a mix?

For an agency managing multiple ecommerce stores on a tight budget, I’d shortlist these:

My pick: omnisend.com

Best overall for your situation. It’s ecommerce-first, supports email + SMS + automation, and has explicit multi-store/agency functionality. Its pricing is also generally more budget-friendly than Klaviyo. Omnisend RealCostLabs

One important 2026 change: SMS is now a Pro add-on for new subscribers, starting at $0.007/SMS for high-volume US sends, so don't assume the old “email + SMS bundled” pricing you may see in older reviews still applies. Omnisend Help Center Omnisend

How I'd rank them

Why I'd avoid standardizing on Klaviyo initially

klaviyo.com is arguably the stronger platform when a client needs sophisticated behavioral segmentation, predictive analytics, and highly customized flows. But you're paying for that depth, and costs can become significant as contact databases grow. Mailercloud RealCostLabs

For an agency, I'd rather have one repeatable Omnisend setup that you can deploy across 10 smaller stores than put every $100k/year client into Klaviyo.

The agency setup I'd use

I'd structure it like this:

• One separate account/store per client — don't mix customer databases.
• Create a standard agency template library: welcome, abandoned cart, browse abandonment, post-purchase, win-back, birthday, review request.
• Create standardized email/SMS campaign templates so your team isn't reinventing creative every week.
• Build a common reporting framework: revenue attributed, revenue/contact, campaign revenue, flow revenue, SMS revenue, unsubscribe rate.
• Put the client's account/payment method on the platform where possible, rather than absorbing software costs into your agency overhead.
• Reserve Klaviyo for clients whose revenue/complexity genuinely justifies it.

Omnisend also currently advertises free migration of contacts, data, segments, flows and templates, which could make moving an existing client roster considerably easier. Omnisend

Bottom line: If your priority is “manage lots of ecommerce clients efficiently without blowing up software costs,” I'd start with Omnisend, then graduate the handful of sophisticated/high-revenue accounts to Klaviyo when they actually need it.

If you tell me roughly how many stores you manage + average subscriber count per store + Shopify/WooCommerce/etc., I can work out the cheapest practical stack and approximate monthly cost for your agency.

Why I'd avoid standardizing on Klaviyo initially

klaviyo.com is arguably the stronger platform when a client needs sophisticated behavioral segmentation, predictive analytics, and highly customized flows. But you're paying for that depth, and costs can become significant as contact databases grow. mailercloud.com RealCostLabs

For an agency, I'd rather have one repeatable Omnisend setup that you can deploy across 10 smaller stores than put every $100k/year client into Klaviyo.

For an agency managing multiple ecommerce shops on a tight budget, I’d shortlist these three:

1. omnisend.com — my pick

This is probably the best fit for your use case.

• Built specifically for ecommerce: email, SMS, automations, abandoned cart, post-purchase, product recommendations, etc.
• Multi-store management lets you switch between client stores from one login. Omnisend Help Center Omnisend
• You can reuse templates, workflows and segments across stores, which is particularly valuable for an agency. Omnisend
• Omnisend has an agency/partner setup and lets agencies create reusable templated accounts for client stores. Omnisend Help Center
• Current Standard pricing starts around $11.20/month, while Pro starts around $41.30/month; SMS is available on Pro for newer subscriptions, starting at $0.007/SMS in the US at high-volume rates. Omnisend

Big caveat: each store still has its own subscription, so this isn't one cheap subscription covering unlimited clients. Omnisend Help Center

2. klaviyo.com — best if clients are willing to pay more

Klaviyo is stronger if sophisticated segmentation, personalization and reporting are important.

It supports multiple accounts under one login, and its shared billing feature can pool email/SMS usage across related accounts. Self-serve shared billing supports up to 20 accounts. Klaviyo Help Center Klaviyo Help Center

The downside for a budget-conscious agency is that Klaviyo generally gets expensive faster as client databases grow. I'd choose it for higher-value clients rather than making it your default stack for every small shop.

3. brevo.com — cheapest general-purpose option

Brevo is worth considering if your clients don't need extremely ecommerce-specific functionality.

Its free plan currently includes 300 email sends/day, email + SMS campaigns, and up to 100,000 stored contacts, although automation is limited. Brevo Help

It's attractive on price, but I'd put it behind Omnisend for a Shopify/ecommerce agency because Omnisend's workflows and multi-store functionality are much more directly designed around ecommerce.

What I'd do in your shoes

I'd standardize the agency on Omnisend, particularly if most of your clients are Shopify/WooCommerce/BigCommerce stores. The ability to build a campaign/automation once and reuse it across client stores can save considerably more agency labor than simply choosing the software with the lowest monthly subscription. Omnisend Omnisend Help Center

One important architectural decision: don't put unrelated clients into one shared customer database. Keep each shop as its own Omnisend store/account while giving your agency team appropriate access. Omnisend specifically supports both the agency-style separate-account model and a master account with multiple stores. Omnisend Help Center

If you tell me roughly how many shops you manage (e.g. 5, 20, 50), average contacts per shop, and monthly SMS volume, I can work out the cheapest setup and compare the likely monthly cost of Omnisend vs. Klaviyo vs. Brevo.

For an agency managing multiple ecommerce shops on a tight budget, I’d shortlist these:

🥇 My pick: Omnisend

For an agency, Omnisend is probably the sweet spot.

It lets you manage multiple stores from one login, switch between stores, and reuse templates, workflows, and segments across stores. It explicitly supports agency/partner setups with separate accounts when clients need separate ownership or billing. Omnisend Help Center Omnisend

The important caveat: each store still has its own subscription—you don't get one cheap subscription covering all your clients. Omnisend Help Center

For new customers in 2026, SMS is on the Pro plan, with SMS priced separately and starting at $0.007/message at qualifying volume. Omnisend Help Center Omnisend Help Center

That's particularly attractive if your shops are Shopify/WooCommerce-style ecommerce businesses because Omnisend is built around ecommerce events: abandoned carts, post-purchase, product recommendations, segmentation, etc.

When I'd choose Klaviyo instead

Klaviyo is the better choice if your clients care heavily about sophisticated segmentation, attribution, and advanced lifecycle marketing.

Its multi-account functionality is quite good: one login can switch between multiple client/store accounts, and Klaviyo also offers shared billing, where up to 20 self-serve accounts can draw from a pooled email/SMS allocation. Klaviyo Help Center Klaviyo Help Center

That shared-billing feature is potentially very interesting for an agency, because clients with uneven list sizes/usage can share a pool rather than each account being completely isolated.

The downside is that Klaviyo can get expensive quickly, so I'd only choose it if you're actually using its more advanced capabilities.

When I'd choose Brevo

Brevo is worth considering if minimizing software cost is the overriding priority.

Its free plan includes email and SMS campaigns, with 300 email sends/day and up to 100,000 stored contacts; paid plans start at $9/month. Brevo Help

I'd rank it behind Omnisend for a pure ecommerce agency, though. Omnisend's multi-store and ecommerce-specific workflow functionality is a closer match to what you're describing.

What I'd do in your position

I'd standardize the agency around Omnisend, unless you have a compelling reason to use Klaviyo.

A practical setup would be:

• One agency master login/account
• Each client/shop as its own store
• Shared agency templates for welcome, abandoned cart, post-purchase, win-back, etc.
• Client-specific branding and segments
• Agency team members given store-specific permissions
• Client pays their own store's subscription/SMS usage
• Reuse your proven flows across every new client

Omnisend specifically supports copying templates, workflows, and segments between stores, which could save your team a lot of repetitive setup work. Omnisend Help Center

Bottom line:
Omnisend → best balance of agency management + ecommerce features + cost.
Klaviyo → best if sophisticated CRM/analytics justify the extra spend.
Brevo → best if absolute software cost is the priority.

If you tell me roughly how many shops you manage, average contacts per shop, and monthly email/SMS volume, I can work out which one is likely to be cheapest for your agency.

For new customers in 2026, SMS is on the Pro plan, with SMS priced separately and starting at $0.007/message at qualifying volume. Omnisend Help Center Omnisend Help Center

That's particularly attractive if your shops are Shopify/WooCommerce-style ecommerce businesses because Omnisend is built around ecommerce events: abandoned carts, post-purchase, product recommendations, segmentation, etc.

When I'd choose Klaviyo instead

Klaviyo is the better choice if your clients care heavily about sophisticated segmentation, attribution, and advanced lifecycle marketing.

Its multi-account functionality is quite good: one login can switch between multiple client/store accounts, and Klaviyo also offers shared billing, where up to 20 self-serve accounts can draw from a pooled email/SMS allocation. Klaviyo Help Center Klaviyo Help Center

That shared-billing feature is potentially very interesting for an agency, because clients with uneven list sizes/usage can share a pool rather than each account being completely isolated.

The downside is that Klaviyo can get expensive quickly, so I'd only choose it if you're actually using its more advanced capabilities.

When I'd choose Brevo

Brevo is worth considering if minimizing software cost is the overriding priority.

Its free plan includes email and SMS campaigns, with 300 email sends/day and up to 100,000 stored contacts; paid plans start at $9/month. Brevo Help

I'd rank it behind Omnisend for a pure ecommerce agency, though. Omnisend's multi-store and ecommerce-specific workflow functionality is a closer match to what you're describing.

What I'd do in your position

I'd standardize the agency around Omnisend, unless you have a compelling reason to use Klaviyo.

A practical setup would be:

• One agency master login/account
• Each client/shop as its own store
• Shared agency templates for welcome, abandoned cart, post-purchase, win-back, etc.
• Client-specific branding and segments
• Agency team members given store-specific permissions
• Client pays their own store's subscription/SMS usage
• Reuse your proven flows across every new client

Omnisend specifically supports copying templates, workflows, and segments between stores, which could save your team a lot of repetitive setup work.

For an agency managing multiple ecommerce stores on a tight budget, I’d shortlist these:

🥇 My pick: Omnisend

Omnisend is probably the best match for your situation.

It specifically supports multiple stores under one account, lets your team switch between stores without logging in/out, and allows you to reuse templates, workflows, and segments between stores. It also supports separate user permissions—useful when several agency employees are working across clients. Omnisend Help Center Omnisend

Most importantly, it's designed around ecommerce data: products, orders, customers, abandoned carts, post-purchase behavior, etc. Omnisend Help Center

The catch is that each store has its own subscription, so you're not getting one cheap plan that covers all your clients. Omnisend Help Center And as of 2026, SMS is primarily on the Pro tier for newer subscriptions, with SMS charged separately based on volume. Omnisend Help Center

omnisend.com

💰 Cheapest: Brevo

Brevo is worth considering if keeping the agency's software bill extremely low is the priority.

Its free plan includes email and SMS campaigns, although email is limited to 300 sends/day. Paid plans start at $9/month for Starter and $18/month for Standard according to Brevo's current pricing information. Brevo Help

The downside is that it's less ecommerce-specialized than Omnisend/Klaviyo. If your clients depend heavily on sophisticated product recommendations, purchase-based segmentation and ecommerce flows, I'd favor Omnisend.

brevo.com

🏆 For higher-value clients: Klaviyo

Klaviyo is what I'd use when a client is big enough that incremental revenue matters more than software cost.

Klaviyo requires a separate account for each ecommerce store, but you can manage multiple accounts from one login. It also supports shared billing across related accounts, pooling email/SMS usage; self-serve shared billing supports up to 20 accounts. Klaviyo Help Center Klaviyo Help Center

That's attractive for an agency, but I'd generally avoid putting every small client on Klaviyo—it can become unnecessarily expensive.

klaviyo.com

What I'd actually do as an agency

I'd use a two-tier stack:

• Small/low-revenue clients: Omnisend or Brevo
• Growing ecommerce clients: Omnisend
• High-revenue / sophisticated Shopify clients: Klaviyo
• Agency-wide templates: maintain a master library of welcome, abandoned-cart, browse-abandonment, post-purchase, win-back, promotional, and SMS flows that you adapt per brand.

If you're managing 10–50+ shops, I'd lean particularly strongly toward Omnisend, because its multi-store functionality was explicitly built around this sort of setup. It currently supports up to 500 stores under one account, while keeping each store's contacts, workflows and reporting separate. Omnisend Help Center

If you tell me roughly how many stores you manage, average contacts per store, and whether they're mostly Shopify/WooCommerce, I can work out which option would likely be cheapest for your agency at that scale.

Most importantly, it's designed around ecommerce data: products, orders, customers, abandoned carts, post-purchase behavior, etc. Omnisend Help Center

The catch is that each store has its own subscription, so you're not getting one cheap plan that covers all your clients. Omnisend Help Center And as of 2026, SMS is primarily on the Pro tier for newer subscriptions, with SMS charged separately based on volume. Omnisend Help Center

omnisend.com

💰 Cheapest: Brevo

Brevo is worth considering if keeping the agency's software bill extremely low is the priority.

Its free plan includes email and SMS campaigns, although email is limited to 300 sends/day. Paid plans start at $9/month for Starter and $18/month for Standard according to Brevo's current pricing information. Brevo Help

The downside is that it's less ecommerce-specialized than Omnisend/Klaviyo. If your clients depend heavily on sophisticated product recommendations, purchase-based segmentation and ecommerce flows, I'd favor Omnisend.

brevo.com

🏆 For higher-value clients: Klaviyo

Klaviyo is what I'd use when a client is big enough that incremental revenue matters more than software cost.

Klaviyo requires a separate account for each ecommerce store, but you can manage multiple accounts from one login. It also supports shared billing across related accounts, pooling email/SMS usage; self-serve shared billing supports up to 20 accounts. help.klaviyo.com help.klaviyo.com

That's attractive for an agency, but I'd generally avoid putting every small client on Klaviyo—it can become unnecessarily expensive.

If you're an agency managing multiple ecommerce stores, I'd prioritize low cost per client + easy account separation + reusable automations/templates + both email and SMS.

My shortlist

1. omnisend.com — my first choice

For your particular setup, I'd probably start here.

Omnisend is ecommerce-first, supports email + SMS in the same marketing workflows, and is generally cheaper than Klaviyo at comparable list sizes. Current published pricing shows Standard starting around $16/month, with substantially lower prices than Klaviyo as contact counts grow. Omnisend RealCostLabs

Why I like it for an agency:

• Separate stores can have their own customer databases and campaigns.
• Ecommerce integrations and prebuilt flows make client onboarding faster.
• Good abandoned-cart, welcome, post-purchase and win-back automation.
• Email + SMS can be coordinated rather than maintained as two systems.
• Lower software cost makes it easier to maintain healthy margins across smaller clients.

Caveat: SMS pricing/availability changed in 2026, so don't evaluate Omnisend based on old articles saying SMS is bundled into the basic plan. New customers generally need Pro for SMS, with SMS credits purchased separately. Omnisend RealCostLabs

2. brevo.com — best if cost is absolutely paramount

Brevo is worth considering if you're managing lots of small stores whose lists aren't huge.

Its pricing is based more heavily on email volume rather than simply the size of the database, and SMS can be purchased separately. Current U.S. SMS pricing starts around $1.09/100 credits. Omnisend

The downside is that it's less ecommerce-specialized than Omnisend/Klaviyo. If you're building sophisticated Shopify customer segments and revenue-driven flows for clients, I'd rather use Omnisend.

3. klaviyo.com — best when clients can afford it

Klaviyo is still the premium choice for serious ecommerce marketing. Its Shopify/WooCommerce data integration, segmentation, analytics and behavioral automation are excellent. TechSifted SMB Compare

But for an agency on a tight budget, there's a problem: you're paying for that sophistication across every client account.

At 10,000 contacts, for example, current comparisons put Klaviyo around $150/month for email versus about $132 for Omnisend Standard, before considering the broader agency economics of having many accounts. Omnisend

I'd use Klaviyo when a client's revenue justifies it—not as the default platform for every small shop.

What I'd do as an agency

I'd actually standardize your stack like this:

Small/new client → Omnisend
Growing client with complex segmentation → Klaviyo
Extremely price-sensitive client → Brevo

More importantly, I'd create a master agency playbook rather than reinventing campaigns for each store:

• Welcome series
• Abandoned cart
• Browse abandonment
• Post-purchase
• Product review request
• Cross-sell
• Win-back
• VIP/customer appreciation
• SMS promotional campaigns
• Email/SMS suppression rules
• Monthly campaign calendar

That way your agency is selling a repeatable ecommerce retention system, rather than hours of email marketing labor.

One important consideration: if by "shared" you mean one central dashboard where your team can manage all clients/stores under one agency login, rather than simply using the same software across separate accounts, that's a different requirement. I can compare the best agency/multi-account setups specifically, including which platforms let you manage 10–50 Shopify stores without paying for unnecessary seats/accounts.

3. klaviyo.com — best when clients can afford it

Klaviyo is still the premium choice for serious ecommerce marketing. Its Shopify/WooCommerce data integration, segmentation, analytics and behavioral automation are excellent. techsifted.com smbcompare.com

But for an agency on a tight budget, there's a problem: you're paying for that sophistication across every client account.

At 10,000 contacts, for example, current comparisons put Klaviyo around $150/month for email versus about $132 for Omnisend Standard, before considering the broader agency economics of having many accounts.

I'd use Klaviyo when a client's revenue justifies it—not as the default platform for every small shop.

What I'd do as an agency

I'd actually standardize your stack like this:

Small/new client → Omnisend
Growing client with complex segmentation → Klaviyo
Extremely price-sensitive client → Brevo

For an agency managing multiple ecommerce stores on a tight budget, I’d prioritize platforms that let you manage multiple stores/accounts without forcing you into an expensive enterprise setup.

My shortlist

1. Omnisend — my pick

This is probably the best fit for your agency.

The big advantage is that Omnisend supports multiple stores under one account, with store switching, centralized billing, shared content assets, and user permissions. It reportedly supports up to 500 stores in one account, which is unusually well suited to an agency model. Omnisend

It also combines email, SMS, automation, segmentation, abandoned-cart flows, popups, etc. rather than making you stitch together separate systems.

Current pricing starts around $16/month for Standard; Pro starts at $59/month, with SMS now charged separately on newer Pro subscriptions. Omnisend Help Center

Why I'd choose it: one operational environment for lots of stores, while still being genuinely ecommerce-focused.

omnisend.com

2. Brevo — cheapest flexible option

Brevo is interesting if your stores have large lists but relatively modest sending volume. Its pricing is primarily based on email volume rather than contacts, and it offers SMS as well. Current entry pricing starts around $9/month. Omnisend

The catch: some of the more sophisticated ecommerce functionality sits behind higher tiers, so the apparent cheapness can disappear as your requirements grow.

I'd use it when: a client mostly needs newsletters, basic automations and SMS rather than sophisticated ecommerce lifecycle marketing.

brevo.com

3. Klaviyo — best, but probably not for your budget

Klaviyo is excellent if you're doing serious behavioral segmentation, predictive analytics and complex customer journeys. But its pricing can climb quickly as each store's active profile count grows. For example, current pricing is around $100/month for 5,000 profiles and $150/month at 10,000, before considering additional messaging needs. Omnisend

The bigger problem for an agency is that Klaviyo doesn't give you the same multiple-store-in-one-account model that Omnisend does. Omnisend

I'd reserve Klaviyo for your larger/high-revenue clients where the extra sophistication can actually pay for itself.

klaviyo.com

What I'd do in your shoes

I'd standardize the agency around Omnisend:

• Omnisend account → multiple client stores
• Give your team appropriate permissions
• Build a library of reusable welcome, abandoned-cart, post-purchase and win-back flows
• Create reusable campaign templates
• Keep each client's audiences/data isolated by store
• Charge clients a monthly management fee on top of their platform/SMS costs

That gives you a much cleaner agency operation than having 10–30 separate Klaviyo environments.

One important caveat: don't choose solely on the platform's advertised starting price. With multiple stores, the real cost depends heavily on each client's contact count, sending frequency and SMS volume. Omnisend's pricing also automatically adjusts based on billable contacts. Omnisend Help Center

If you tell me roughly how many shops you manage, average contacts per shop, and whether they're mostly Shopify/WooCommerce, I can work out the cheapest agency stack and estimated monthly cost for you.

My shortlist

For an agency managing multiple ecommerce shops on a tight budget, I’d prioritize:

1. One dashboard / easy client switching
2. Separate customer data per store
3. Reusable flows and templates
4. Reasonable SMS costs
5. Client reporting you can hand off

My shortlist:

My recommendation for your situation

If most of your shops are Shopify and ecommerce-focused:

• Default stack: Omnisend
• Upgrade clients: Klaviyo
• Tiny-budget clients: Brevo

That gives you a service ladder:

• $0–$1k/month clients → Brevo or Omnisend
• Growing brands → Omnisend
• Serious DTC brands → Klaviyo

Agency workflow I’d set up

• Create a master library of: - Welcome series
• Abandoned cart
• Browse abandonment
• Post-purchase cross-sell
• Win-back
• VIP/customer anniversary flows
• Duplicate and customize per store
• Keep each shop’s sending domains, lists, and analytics isolated
• Charge clients a management fee + pass through SMS spend

One thing I’d avoid: putting all brands into one shared subscriber database. It creates deliverability, consent, and reporting headaches.

If you’re managing 5–20 stores, I’d lean Omnisend or MailFlow. If you’re managing larger Shopify brands, I’d standardize on Klaviyo and build your agency processes around it. MailFlow SoftwareInspect

I can also help you design a low-cost agency stack (platform + client billing + templates + reporting) if you share roughly how many shops you manage and what platforms they run on (Shopify, WooCommerce, etc.).

For an agency managing multiple ecommerce stores on a tight budget, I’d shortlist these three:

1. Omnisend — my first choice

• Built specifically for ecommerce email + SMS.
• Supports multiple stores under one account, with easy store switching and the ability to reuse templates/workflows across stores. Omnisend Omnisend Help Center
• Current Pro pricing starts at $59/month per store, with SMS available separately from $0.007/message in the US/Canada at the entry volume tier. Omnisend Help Center
• The catch: each store is billed separately, so it doesn't literally give you one cheap subscription for unlimited clients. Omnisend Help Center
• omnisend.com
• Sendlane — worth considering for high-volume clients

• Particularly interesting if some of your stores have large databases because its pricing is based on send volume rather than profiles, with unlimited profiles. Sendlane
• Email + SMS are available, and its Agency tier is specifically designed for larger/multi-account operations. Sendlane
• Could become considerably more economical than contact-based pricing as lists get large.
• sendlane.com
• Klaviyo — best capabilities, not my budget pick

• Excellent segmentation, automation and ecommerce integrations.
• It supports multiple accounts accessible from one login, which is useful for agencies. Klaviyo Help Center
• But for a tight-budget agency, I'd generally choose Omnisend unless a client needs Klaviyo's more sophisticated capabilities.
• klaviyo.com

What I'd do in your situation

Use Omnisend as the agency standard, unless your clients have unusually large contact lists.

The important distinction is that you don't necessarily want a "shared mailing list" across clients—you want one agency login/workspace where your team can efficiently operate separate stores, while keeping each client's contacts, domains, reporting and automations isolated.

Omnisend is unusually well suited to that workflow: you can have multiple stores under the account, switch between them, assign roles, and reuse templates/workflows. Omnisend Omnisend Help Center

If you tell me roughly how many shops you manage + average contacts per shop + monthly email/SMS volume, I can work out which option would be cheapest and give you an estimated monthly agency-wide cost.

For an agency managing multiple ecommerce stores on a tight budget, I’d shortlist these:

1. omnisend.com — my first choice

• Specifically built for ecommerce email + SMS.
• Lets you manage multiple stores from one account and switch between them without separate logins.
• Templates and workflows can be reused across stores, which is particularly useful for an agency. Omnisend Help Center Omnisend
• Current pricing starts at $16/mo per store for Standard; SMS requires Pro for new subscribers, with Pro starting at $59/mo and SMS charged separately. Omnisend Help Center
• Best fit: lots of small/mid-sized Shopify or ecommerce clients where you want repeatable campaigns and automations without Klaviyo-level costs.
• klaviyo.com — best if clients can afford it

• More sophisticated customer data, segmentation, attribution, and automation.
• Excellent if you're doing advanced lifecycle marketing for larger DTC brands.
• But costs rise considerably with contact volume; email + SMS is an additional expense. Omnisend
• Best fit: fewer, higher-value clients where the additional capabilities can directly generate enough revenue to justify the cost.
• mailerlite.com — cheapest/simple option

• Worth considering when clients primarily need newsletters, basic automations and landing pages.
• I'd choose it over Omnisend for very simple campaigns, but not if sophisticated ecommerce triggers and SMS are central to your service.

What I'd do as an agency

I'd standardize on Omnisend unless you have clients with unusually sophisticated data/segmentation requirements.

The important distinction is that Omnisend's multi-store setup doesn't mean one subscription covers all your stores: each store has its own data and subscription/billing. However, the agency can centrally access the stores and reuse templates/workflows. Omnisend Help Center

That makes it a good operational model:

Agency account → Store A / Store B / Store C → reusable campaign templates + automation recipes

You could build a standardized library such as:

• Welcome series
• Abandoned cart
• Browse abandonment
• Post-purchase
• Win-back
• Product launch
• Promotional SMS
• Holiday campaign templates

Then customize branding, products, audiences and offers for each client rather than rebuilding everything.

One caveat: if by "shared" you mean one central database where you can send campaigns across multiple completely separate shops/brands from a single audience, that's a different requirement. Omnisend keeps each store's customer data separate. Omnisend Help Center

If you tell me roughly how many shops you manage (e.g. 5, 20, 50), average contacts per shop, and monthly email/SMS volume, I can work out which platform would likely be cheapest in total for your agency.

For an agency managing multiple ecommerce shops on a tight budget, I would optimize for:

• One team workspace (multiple brands/stores)
• Easy client separation (no sending Brand A campaigns to Brand B)
• Reusable flows/templates
• Affordable contact-based pricing
• Email + SMS in the same platform
• Good ecommerce integrations (Shopify/WooCommerce/etc.)

My shortlist:

1. omnisend.com — Best budget choice for most agencies

Best fit: agencies managing several small-to-mid ecommerce brands.

Why I’d consider it first:

• Built specifically for ecommerce email + SMS.
• Strong prebuilt automations (welcome, abandoned cart, post-purchase, win-back).
• Generally positioned as a lower-cost alternative to Klaviyo. Omnisend AutoMarketer
• Supports major ecommerce platforms including Shopify, WooCommerce, BigCommerce, and others. Omnisend

Agency workflow:

• Create one account per client/store (clean separation).
• Maintain a shared library of: - abandoned cart flows
• welcome series
• promotional templates
• segmentation rules
• reporting dashboards

Downside: less advanced than Klaviyo for very sophisticated lifecycle marketing.

2. klaviyo.com — Best if clients are higher-value brands

Best fit: DTC brands doing serious revenue where retention strategy matters.

Strengths:

• Excellent customer data model.
• Very powerful segmentation.
• Strong Shopify ecosystem.
• Better for complex flows like: - VIP programs
• predictive segments
• multi-product lifecycle journeys

Klaviyo does have a free entry tier, but costs can rise as lists grow. Klaviyo DE

Agency concern: if you manage 10–20 stores, per-brand subscriptions can become expensive.

3. brevo.com — Cheapest general-purpose option

Best fit: smaller shops where advanced ecommerce automation is not the priority.

Pros:

• Usually cheaper at lower volumes.
• Good for newsletters, basic automation, SMS.
• Useful if some clients are not heavily ecommerce-driven.

Cons:

• Ecommerce segmentation and revenue attribution are weaker than Omnisend/Klaviyo.

4. mailchimp.com — Familiar but not my first choice for ecommerce

Good:

• Clients recognize it.
• Lots of integrations.
• Easy for simple campaigns.

Less ideal:

• Ecommerce automation is not as purpose-built as Omnisend/Klaviyo.
• Agencies often outgrow it once stores need serious retention marketing.

How I’d structure this as an agency

I would avoid putting all stores into one giant account. Instead:

Agency master process

• One account/workspace per client brand.
• Shared internal template library.
• Standard automation package: 1. Welcome series
• Abandoned cart
• Browse abandonment
• Post-purchase upsell
• Review request
• Win-back campaign
• Monthly promotional calendar

My pick by client type:

For a budget-conscious agency managing multiple shops, I’d start with Omnisend as the default stack, keep Klaviyo as a premium upsell, and avoid paying enterprise ESP prices until a client’s revenue justifies it. Omnisend Klaviyo DE

If you tell me roughly how many stores you manage (5, 20, 100+) and whether they’re mostly Shopify, I can suggest an agency setup and estimated monthly software cost.

For an agency managing multiple ecommerce shops on a tight budget, I’d prioritize platforms that let your team manage multiple stores without buying a completely separate tool stack for every client.

My shortlist

🥇 I'd start with Omnisend

For your specific situation, Omnisend is probably the sweet spot.

It explicitly supports multiple stores under one account, with the ability to switch between stores, reuse templates/workflows, and manage different user permissions. It supports up to 500 stores under one account. Importantly for an agency, Omnisend also supports separate accounts when clients need their own ownership/billing. Omnisend Help Center Omnisend

The catch is that each store still has its own subscription, so you're not literally paying one flat agency fee for all clients. Omnisend Help Center

For new subscribers, Omnisend's current pricing has SMS on Pro, starting at $59/month, with SMS priced separately based on volume; its published U.S. SMS rates start at $0.007/message at higher volumes. Omnisend Help Center Omnisend

That makes it particularly attractive if you're standardizing a repeatable agency setup:

Store → Omnisend → reusable welcome flow / abandoned cart / post-purchase / winback → email + SMS

You can build the framework once and adapt it for each shop.

🥈 Klaviyo if the clients are more sophisticated

Klaviyo is the one I'd choose when a client's ecommerce marketing is complex enough to justify the extra cost—lots of segmentation, sophisticated customer data, predictive analytics, or a large integration ecosystem.

Klaviyo supports multiple accounts under one login, which makes switching between client/store accounts reasonably convenient. Klaviyo Help Center

It also has shared billing, where related accounts can pool email/SMS usage under a parent account. However, this requires requesting approval from Klaviyo and is limited to an account-family structure (one parent plus up to 33 child accounts). Klaviyo Help Center

So I'd use Klaviyo selectively rather than automatically putting every small client on it.

🥉 Brevo if absolute cost is the priority

Brevo is worth considering if you're managing smaller shops where advanced ecommerce functionality isn't as important.

Its current plans start at $0, with paid plans starting at $9/month, and it supports email and SMS. The free plan includes 300 email sends/day and up to 100,000 stored contacts. Brevo Help

The tradeoff is that I wouldn't consider it as ecommerce-specialized as Omnisend or Klaviyo. For basic newsletters, promotions, automations and SMS, though, it can be extremely economical.

What I'd actually do as an agency

I'd standardize around two tiers:

• Small/simple shops: Brevo or Omnisend
• Growing/high-value shops: Omnisend
• Sophisticated/high-revenue shops: Klaviyo

If you want one platform for basically everyone, I'd pick Omnisend. Its multi-store architecture is unusually well aligned with what you're describing, and its ability to copy templates, workflows and segments between stores could save your team a lot of labor. Omnisend Help Center

One important distinction: don't create one shared customer database for all your clients. Keep each shop's contacts, consent, purchase history and sending reputation isolated; share your agency's templates/flows/processes, not the customer data.

If you tell me roughly how many shops you manage, average contacts per shop, and monthly email/SMS volume, I can work out which option is likely to be cheapest and give you a concrete agency stack.

The catch is that each store still has its own subscription, so you're not literally paying one flat agency fee for all clients. Omnisend Help Center

For new subscribers, Omnisend's current pricing has SMS on Pro, starting at $59/month, with SMS priced separately based on volume; its published U.S. SMS rates start at $0.007/message at higher volumes. Omnisend Help Center Omnisend

That makes it particularly attractive if you're standardizing a repeatable agency setup:

Store → Omnisend → reusable welcome flow / abandoned cart / post-purchase / winback → email + SMS

You can build the framework once and adapt it for each shop.

🥈 Klaviyo if the clients are more sophisticated

Klaviyo is the one I'd choose when a client's ecommerce marketing is complex enough to justify the extra cost—lots of segmentation, sophisticated customer data, predictive analytics, or a large integration ecosystem.

Klaviyo supports multiple accounts under one login, which makes switching between client/store accounts reasonably convenient. Klaviyo Help Center

It also has shared billing, where related accounts can pool email/SMS usage under a parent account. However, this requires requesting approval from Klaviyo and is limited to an account-family structure (one parent plus up to 33 child accounts). Klaviyo Help Center

So I'd use Klaviyo selectively rather than automatically putting every small client on it.

🥉 Brevo if absolute cost is the priority

Brevo is worth considering if you're managing smaller shops where advanced ecommerce functionality isn't as important.

Its current plans start at $0, with paid plans starting at $9/month, and it supports email and SMS. The free plan includes 300 email sends/day and up to 100,000 stored contacts. Brevo Help

The tradeoff is that I wouldn't consider it as ecommerce-specialized as Omnisend or Klaviyo. For basic newsletters, promotions, automations and SMS, though, it can be extremely economical.

What I'd actually do as an agency

I'd standardize around two tiers:

• Small/simple shops: Brevo or Omnisend
• Growing/high-value shops: Omnisend
• Sophisticated/high-revenue shops: Klaviyo

If you want one platform for basically everyone, I'd pick Omnisend. Its multi-store architecture is unusually well aligned with what you're describing, and its ability to copy templates, workflows and segments between stores could save your team a lot of labor.

For an agency managing multiple ecommerce stores on a tight budget, I’d shortlist these three:

1. Omnisend — my first choice

I'd start here. Omnisend is specifically ecommerce-oriented and lets you put multiple stores under one account, switch between them, and reuse templates/workflows across stores. More importantly for an agency, its Partner Portal lets you create templated accounts and copy campaigns, automations and signup forms into client stores. Omnisend Omnisend Help Center

The current pricing is also attractive: Standard starts at $16/month, while Pro starts at $59/month. For new subscribers, SMS requires Pro and is charged separately, with US/Canada rates starting around $0.009/SMS and falling to $0.007 at higher monthly volumes. Omnisend Help Center Omnisend

The catch: each store has its own subscription, so you don't get one $16 account that covers ten stores. Omnisend Help Center

For an agency, though, the ability to build a "master" automation/template setup and replicate it is a big operational advantage.

2. Klaviyo — best if clients are more sophisticated

klaviyo.com is probably the better choice if your agency is doing serious segmentation, behavioral automation, attribution and lifecycle marketing.

It supports multiple accounts under one login, and its Portfolios give agencies a high-level view across multiple brand accounts. Klaviyo Help Center Klaviyo Help Center

There's also an interesting option for agencies with enough volume: Klaviyo Shared Billing can put multiple related accounts into an account family that shares a pool of email/SMS sends. Klaviyo says an account family can have one parent plus up to 33 child accounts, although shared billing requires approval from Klaviyo. Klaviyo Help Center

That's potentially very compelling for an agency, but I'd only choose Klaviyo if the additional capabilities justify the higher cost/complexity.

3. Brevo — best ultra-budget alternative

brevo.com is worth considering if your clients don't need the depth of ecommerce-specific automation.

Its free plan includes email and SMS campaigns, although email is limited to 300 sends/day. Paid plans start at $9/month. Brevo Help

The tradeoff is that I'd consider it more of a general marketing/CRM platform with ecommerce capabilities than an ecommerce-native lifecycle platform like Omnisend or Klaviyo.

What I'd do in your position

For 5–20+ small Shopify/WooCommerce stores:

Omnisend → one store per client → agency master templates → clone/reuse automations.

I'd build a standardized library of:

• Welcome series
• Abandoned cart
• Browse abandonment
• Post-purchase
• Cross-sell
• Win-back
• Review request
• VIP/customer segmentation
• Promotional email + SMS campaigns

Then customize branding, products, offers and segmentation per client.

If you're managing enough volume to negotiate consolidated billing, I'd investigate Klaviyo's shared-billing setup before committing. It could materially change the economics for a larger agency. Klaviyo Help Center

If you tell me roughly how many stores you manage, average contacts per store, and whether they're mostly Shopify, I can work out which of these would likely be cheapest per client/month, including SMS.

For an agency, though, the ability to build a "master" automation/template setup and replicate it is a big operational advantage.

2. Klaviyo — best if clients are more sophisticated

klaviyo.com is probably the better choice if your agency is doing serious segmentation, behavioral automation, attribution and lifecycle marketing.

It supports multiple accounts under one login, and its Portfolios give agencies a high-level view across multiple brand accounts. Klaviyo Help Center Klaviyo Help Center

There's also an interesting option for agencies with enough volume: Klaviyo Shared Billing can put multiple related accounts into an account family that shares a pool of email/SMS sends. Klaviyo says an account family can have one parent plus up to 33 child accounts, although shared billing requires approval from Klaviyo. Klaviyo Help Center

That's potentially very compelling for an agency, but I'd only choose Klaviyo if the additional capabilities justify the higher cost/complexity.

3. Brevo — best ultra-budget alternative

brevo.com is worth considering if your clients don't need the depth of ecommerce-specific automation.

Its free plan includes email and SMS campaigns, although email is limited to 300 sends/day. Paid plans start at $9/month. help.brevo.com

The tradeoff is that I'd consider it more of a general marketing/CRM platform with ecommerce capabilities than an ecommerce-native lifecycle platform like Omnisend or Klaviyo.

What I'd do in your position

For 5–20+ small Shopify/WooCommerce stores:

Omnisend → one store per client → agency master templates → clone/reuse automations.

I'd build a standardized library of:

For an agency managing multiple ecommerce shops on a tight budget, I’d shortlist these:

1. Omnisend — my first choice

This is probably the sweet spot for an agency like yours.

Omnisend explicitly supports multiple stores under one account, with the ability to switch between stores, control user permissions by store, and—particularly useful for an agency—copy templates, workflows and segments between stores. It supports up to 500 stores under one account. Omnisend Help Center Omnisend

The important catch is that each store is billed separately based on its contacts, so you don't get one giant shared contact pool. Omnisend Help Center

For new customers, SMS is currently available on the Pro plan, with US/Canada SMS starting at $0.007/message at high volume. The Pro plan currently starts around $59/month at the standard list price, although the exact cost scales with contacts. Omnisend Help Center Omnisend

Why I'd pick it for an agency: you can build a good abandoned-cart/welcome/post-purchase framework once, then adapt it across clients instead of rebuilding everything.

omnisend.com

2. Brevo — if minimizing software costs is priority #1

Brevo is worth considering if your clients don't need extremely deep ecommerce segmentation.

Its free plan includes email and SMS campaigns, with up to 100,000 stored contacts and 300 email sends/day. Paid plans start at $9/month. Brevo Help

The downside is that I wouldn't choose it over Omnisend for a Shopify-heavy agency where you're doing sophisticated ecommerce automation. Omnisend is more purpose-built around ecommerce behaviors such as browsing, purchases, cart abandonment and product recommendations. Omnisend

3. Klaviyo — best, but harder to justify on a tight budget

Klaviyo is the one I'd use when a client's revenue justifies it.

It supports multiple accounts accessible through one login, which works well when you manage several brands/stores. Klaviyo Help Center It also has shared billing, where related accounts can potentially share a pool of email/SMS sends, although you have to request it and Klaviyo approves it case-by-case. Klaviyo Help Center

Its big advantage is the depth of segmentation, analytics, personalization and automation. Its disadvantage for your situation is simply cost and complexity.

What I'd actually do

I'd standardize the agency around Omnisend and create a reusable "agency playbook":

• Welcome series
• Abandoned cart
• Browse abandonment
• Post-purchase
• Cross-sell
• Win-back
• VIP/customer segmentation
• Email campaign templates
• SMS campaign templates
• Monthly reporting template

Then each new shop gets a copy of the base system with its branding, products and audience rules swapped in.

That gives you one team's operating system for multiple clients, rather than having your staff learn and maintain three different platforms.

One particularly nice agency feature is that Omnisend allows separate client accounts while letting shared users transfer templates, automations and segments between accounts—useful when each client needs their own billing/ownership. Omnisend Help Center

My ranking for you: Omnisend → Brevo → Klaviyo.

If you tell me roughly how many shops you manage, average contacts per shop, and monthly email/SMS volume, I can work out which one is likely to be cheapest and give you an approximate monthly agency software bill.

For an agency managing multiple ecommerce shops on a tight budget, I’d prioritize platforms that let you centralize client access, reuse campaigns/automations, and handle email + SMS without paying for a separate tool per channel.

My shortlist

1. Omnisend — my first choice

This is probably the best fit for what you're describing.

Omnisend supports multiple stores under one account, lets your team switch between stores, and—particularly useful for an agency—allows you to copy templates, workflows and segments between stores. It also has a Partner Portal for managing client accounts and reusable templated accounts. Omnisend Help Center Omnisend Help Center Omnisend Help Center

It combines email, SMS and push rather than making you stitch together separate tools. Omnisend

The catch is that each store still has its own subscription, so "one account" doesn't mean one subscription for all your clients. Omnisend Help Center

Current pricing starts at $16/month for Standard and $59/month for Pro; importantly, SMS on new subscriptions requires Pro, with SMS starting at $0.007/message in the US/Canada. Omnisend Help Center

Why I'd pick it: You can build a standard abandoned-cart flow, welcome series, post-purchase flow, etc. once and replicate the framework across your Shopify clients.

2. Brevo — best if cost is the overriding concern

brevo.com is worth serious consideration if your clients have relatively modest ecommerce marketing requirements.

Its free plan includes email and SMS campaigns, with 300 email sends/day, and paid plans start at $9/month. Brevo Help

More importantly for an agency, Brevo has centralized multi-account management through its agency program, so your team can switch between client accounts rather than maintaining an entirely separate agency login for each one. Brevo

Why I'd pick it: If you're managing, say, 10–30 small shops and margins are tight, Brevo can keep software costs substantially lower.

The downside is that it's less ecommerce-specialized than Omnisend/Klaviyo.

3. Klaviyo — best, but probably not your budget option

klaviyo.com is the one I'd choose if your clients are sophisticated DTC brands and you're doing serious segmentation, attribution and lifecycle marketing.

It also has an interesting shared-billing capability: related accounts can potentially share a pool of email/SMS sends under one billing plan, subject to Klaviyo approval. Klaviyo Help Center

But for an agency explicitly trying to keep costs down, I'd generally start with Omnisend or Brevo and only move clients to Klaviyo when the additional sophistication actually pays for itself.

What I'd do in your shoes

I'd use Omnisend as the agency standard and create a repeatable "client starter kit":

• Welcome series
• Abandoned cart
• Browse abandonment
• Post-purchase
• Win-back
• Review request
• Email campaigns
• SMS campaigns
• Signup forms
• Standard segmentation
• Reporting template

Then customize branding, products, offers and tone for each shop.

Omnisend's new templated-account functionality is particularly suited to this agency workflow: you can create reusable campaigns, automations and signup forms and copy them into client stores. Omnisend Help Center

If your average client has fewer than ~1,000–2,000 contacts and you're extremely price-sensitive, I'd also price out Brevo before committing. If they're Shopify-heavy and ecommerce revenue is the priority, I'd lean Omnisend.

If you tell me roughly how many shops you manage, average contacts per shop, and whether they're mostly Shopify/WooCommerce/BigCommerce, I can work out which setup is likely to be cheapest—including the approximate monthly agency software cost.

For an agency managing multiple ecommerce stores on a tight budget, I’d prioritize:

1. One master platform your team can learn once
2. Separate client workspaces/accounts
3. Affordable scaling as lists grow
4. Strong ecommerce automations (welcome, abandoned cart, post-purchase, winback)
5. Email + SMS in the same workflow

My shortlist:

Omnisend Help Center Drip## My recommendation for your situation

1. Best overall: Omnisend

For an agency managing several shops, this is probably where I’d start.

Why:

• Built specifically for ecommerce.
• Good Shopify/WooCommerce workflows.
• Email + SMS + push in one system.
• Lower cost ceiling than Klaviyo for many smaller brands.
• Easier for junior account managers to operate.

Omnisend’s paid plans are positioned around ecommerce use cases, with SMS available on higher tiers/add-ons depending on plan timing and region. Omnisend Help Center

A practical agency setup:

• One agency login/team
• One workspace per client store
• Standardized templates: - Welcome series
• Abandoned cart
• Browse abandonment
• Post-purchase upsell
• Review request
• Winback campaign

2. Upgrade path: Klaviyo

Use this when a client is doing serious revenue and needs deeper segmentation.

Best for:

• Shopify brands doing $1M+/year
• Advanced lifecycle marketing
• Complex customer segments
• Clients who care about predictive analytics and detailed attribution

Downside for an agency: costs can climb quickly as client lists grow, especially once SMS is added. Ecommerce Times

I’d avoid putting every small client on Klaviyo unless you can bill enough management fees to cover it.

3. Cheapest option: Brevo

Good if clients have:

• Small lists
• Low SMS volume
• Mostly promotional emails

The tradeoff is that ecommerce automation depth generally isn’t as strong as Omnisend/Klaviyo.

Agency workflow I’d use

Tier clients:

• <$5k/month ecommerce revenue: Omnisend or Brevo
• $5k–$100k/month: Omnisend
• $100k+/month: Klaviyo

Create a reusable “retention stack”:

• 5–7 core automations
• 3 campaign templates
• SMS compliance checklist
• Monthly reporting dashboard

That lets your team onboard stores quickly instead of rebuilding every account.

One thing I’d clarify before choosing: are your shops mostly Shopify, WooCommerce, or a mix? The best choice changes quite a bit depending on the ecommerce platform and how many stores you manage.

Yes. For an agency managing multiple ecommerce shops on a tight budget, I’d prioritize platforms that let you centralize access, reuse campaigns/flows, and avoid paying for a completely separate stack for every store.

My shortlist

1. omnisend.com — my first choice

This is probably the one I'd test first for your agency.

The important feature isn't just email + SMS: Omnisend explicitly supports multiple stores under one account, letting you switch between stores and reuse templates and workflows across them. Omnisend

That is particularly valuable for an agency. You could, for example, build a strong:

• Welcome series
• Abandoned-cart flow
• Browse-abandonment flow
• Post-purchase sequence
• Review request
• Win-back campaign

…and adapt those for each client rather than rebuilding everything.

Pricing is also relatively aggressive. Standard starts around $16/month, while Pro starts around $59/month; importantly, for new subscriptions after May 4, 2026, SMS is on Pro rather than Standard. Omnisend Help Center Omnisend

Why I'd choose it: You get a genuinely ecommerce-focused platform without immediately getting into Klaviyo-level costs.

2. brevo.com — best if absolute cost is priority #1

Brevo has an unusual advantage for agencies: it primarily prices around message volume rather than the size of your contact database. Its free tier can hold up to 100,000 contacts, although sending is limited. Omnisend

That can work very well if your clients have:

lots of contacts + relatively infrequent campaigns.

It supports email, SMS, WhatsApp, transactional messaging and CRM functionality. Omnisend

The tradeoff is that it isn't as ecommerce-specialized as Omnisend or Klaviyo. If you're doing sophisticated Shopify customer segmentation and revenue-attributed flows, I'd lean Omnisend.

3. klaviyo.com — use selectively

Klaviyo is excellent, but I wouldn't make it your default agency platform if you're genuinely budget constrained.

Its strengths are extremely granular ecommerce data, segmentation, customer profiles and sophisticated automation. But pricing is based on active profiles, and SMS is an additional cost layer. Omnisend Ecommerce Times

I'd reserve it for your larger/high-value clients where the additional segmentation and analytics can actually generate enough incremental revenue to justify the expense.

What I'd do if I were your agency

I'd actually use a two-tier stack:

Small/mid-size clients → Omnisend

Larger clients with sophisticated CRM requirements → Klaviyo

And I'd investigate Brevo for clients with unusually large databases but relatively low sending volume.

The big thing I'd avoid is putting every client into Klaviyo by default. At an agency with 10, 20, or 50 stores, relatively small monthly differences become a significant operating expense.

If you tell me roughly how many shops you manage (e.g. 5/20/50), their average subscriber count, and whether they're mostly Shopify, WooCommerce, etc., I can work out which setup would be cheapest and how I'd structure the agency accounts.

For an agency managing multiple ecommerce stores on a tight budget, I’d shortlist these three:

1. My pick: Omnisend

I'd start with Omnisend for an agency like yours.

The important differentiator is that Omnisend explicitly supports multiple stores under one account, lets you switch between stores, and—particularly useful for an agency—allows templates and workflows to be reused across stores. Omnisend Help Center Omnisend

That means you could build things like:

• Welcome series
• Abandoned cart
• Browse abandonment
• Post-purchase
• Win-back
• Promotional email/SMS campaigns

…and then reuse the underlying setup for another client rather than rebuilding everything.

The current pricing is also unusually attractive for smaller stores: Standard starts around $11.20/month for 500 contacts on the pricing page, while Pro starts around $41.30/month for 2,500 contacts and includes unlimited email, with SMS charged separately. US SMS starts at $0.009/message at lower volumes and falls to $0.007 at $10k+ monthly SMS spend. Omnisend

One caveat: new Standard subscriptions don't include SMS; SMS requires Pro under Omnisend's current 2026 pricing. Omnisend Help Center

omnisend.com

2. Klaviyo — better if sophistication matters

Klaviyo would be my choice if your agency is doing serious lifecycle marketing and clients expect sophisticated segmentation, attribution, personalization and reporting.

It supports multiple accounts/stores under one login, and Klaviyo even has shared billing, where related accounts can potentially draw from a shared pool of email/SMS sends. Shared billing requires approval from Klaviyo and is handled case-by-case. Klaviyo Help Center Klaviyo Help Center

The downside for a budget-conscious agency is that Klaviyo can get expensive as the number of client databases grows. I'd be reluctant to put 10–20 small shops into Klaviyo unless the revenue they're generating justifies it.

3. Brevo — worth considering for very small clients

Brevo is worth looking at if many of your clients have relatively small lists and you want inexpensive email/SMS without needing all the ecommerce-specific sophistication of Klaviyo.

I'd put it behind Omnisend for a Shopify-heavy agency, though. The ecommerce automation and multi-store workflow reuse are more directly aligned with what you're describing.

What I'd actually do as an agency

I'd avoid trying to force one giant shared database across all clients. Keep each shop's customer data isolated, but standardize your marketing machinery.

For example:

Agency master playbook

→ Welcome flow
→ Cart abandonment
→ Browse abandonment
→ Post-purchase
→ Cross-sell
→ Win-back
→ VIP/customer segmentation
→ Promotional campaign templates
→ SMS templates
→ Reporting dashboard

Then deploy/customize that framework for each store.

For your particular situation, I'd test Omnisend first. Its multi-store architecture plus reusable templates/workflows is almost tailor-made for an agency managing several ecommerce brands, and the pricing is substantially easier to stomach when you're managing a portfolio of smaller shops. Omnisend Omnisend

If you tell me roughly how many stores you manage, average contacts per store, Shopify/WooCommerce/etc., and approximate monthly email/SMS volume, I can work out which platform would be cheapest for your portfolio rather than just comparing the headline prices.

For an agency managing multiple ecommerce stores on a tight budget, I’d shortlist these:

My pick: Omnisend

omnisend.com is probably the best fit if your clients are primarily Shopify/WooCommerce/BigCommerce stores.

• Built specifically around ecommerce: email, SMS, automations, segmentation, product data, abandoned cart, etc.
• Multiple stores can be managed from one account, so your team can switch between clients without juggling logins. Omnisend Help Center Omnisend
• Their agency Partner Portal now supports templated accounts, letting you build automations, campaigns and signup forms once and copy them to multiple client stores. That's a particularly useful agency feature. Omnisend Help Center
• Pricing is relatively accessible: Standard starts at $16/month, while Pro starts at $59/month; SMS is available on Pro under the current 2026 pricing. Omnisend Help Center
• The catch: each store is billed separately, so you don't get one cheap subscription covering all your clients. Omnisend Help Center

For a small agency, I'd start here.

If you want the most sophisticated option: Klaviyo

klaviyo.com is the stronger choice if your clients are larger brands or you need sophisticated segmentation, attribution and lifecycle automation.

One interesting agency advantage is Klaviyo shared billing: related accounts can potentially draw from a shared pool of email/SMS sends. Klaviyo says an account family can have one parent and up to 33 child accounts, although shared billing requires approval from Klaviyo. Klaviyo Help Center

The downside for your situation is simply cost and complexity. I wouldn't make Klaviyo the default for every small client.

The budget-conscious setup I'd use

There's also an important distinction I'd make: don't necessarily try to put every client's database into one master account. You generally want each store's customers, consent, analytics and ecommerce events isolated. Omnisend explicitly keeps store data, automations, reporting and contacts separate while allowing your agency team to manage the stores centrally. Omnisend Help Center

What I'd do in your shoes

Omnisend as the agency standard → one store/brand per client → reusable agency templates → client-specific lists and automations → client pays the store's subscription.

That gives you a repeatable operating model without paying for a giant agency marketing platform.

If you tell me roughly how many stores you manage, average contacts per store, and whether they're mostly Shopify, I can work out the cheapest setup and approximate monthly cost across Omnisend vs Klaviyo vs Brevo.

For an agency managing multiple ecommerce stores on a tight budget, I’d prioritize:

1. One dashboard for multiple brands/stores
2. Client/user permissions
3. Shared templates, flows, and reporting
4. Email + SMS in the same platform (to avoid duplicated sends and messy attribution)
5. Reasonable scaling costs

My shortlist:

My recommendation for your agency

Primary stack: Omnisend

For a lean agency with many small-to-mid ecommerce clients, I’d start there. The main advantages are:

• Manage multiple stores without building a huge stack
• Run email and SMS together
• Reuse campaign structures and automation templates
• Lower software overhead than putting every small client on premium tooling
• Easier onboarding for junior team members

Omnisend specifically highlights multi-store management, centralized billing, and store switching capabilities, which is a good match for agencies. Omnisend

How I’d structure clients

• <$50k/month revenue stores: Omnisend
• Growing stores with serious retention programs: Klaviyo
• Enterprise/high-volume SMS brands: consider specialized SMS platforms later

A practical agency setup:

• Create reusable templates: - Welcome series
• Abandoned cart
• Browse abandonment
• Post-purchase
• Winback
• VIP/customer appreciation
• Keep each client’s data isolated
• Build a reporting template showing: - Revenue attributed
• Flow revenue
• Campaign revenue
• List growth
• SMS opt-in growth

One question would change the recommendation quite a bit: are these mostly Shopify stores, WooCommerce stores, or a mix?

For an agency managing multiple ecommerce shops on a tight budget, I’d prioritize:

1. Multi-store management
2. Client/user permissions
3. Separate brand assets and lists
4. Affordable SMS costs
5. Reusable flows/templates

My shortlist:

1. Omnisend — best fit for most budget-conscious agencies

omnisend.com

Why I’d put this first:

• Built specifically for ecommerce (Shopify, WooCommerce, BigCommerce, etc.)
• Supports managing multiple stores under one account structure, which is useful for agencies handling many merchants. Omnisend
• Email + SMS + push in one platform
• Strong prebuilt ecommerce flows: - abandoned cart
• welcome series
• post-purchase
• win-back
• Lower cost profile than many enterprise-focused tools. Omnisend

Agency setup I’d use:

• One agency owner account
• Separate store connections per client
• Duplicate proven flows/templates
• Charge clients a monthly management fee + platform pass-through

Downside: Less sophisticated than Klaviyo for extremely complex segmentation.

2. Klaviyo — best if your clients are larger DTC brands

klaviyo.com

Strengths:

• Probably the deepest ecommerce customer segmentation
• Excellent Shopify data model
• Powerful reporting and attribution
• Lots of agency adoption

Weaknesses for your situation:

• Costs can climb quickly across multiple stores
• Each client often ends up needing their own account/billing arrangement
• More setup time per store

I’d use Klaviyo when a client has enough revenue that advanced segmentation pays for itself.

3. Brevo — cheapest general-purpose option

brevo.com

Good if:

• Stores are small
• Campaigns are simple
• You need inexpensive email/SMS rather than advanced ecommerce automation

Less ideal if you rely heavily on product recommendations, purchase behavior, and ecommerce-specific flows.

4. ActiveCampaign — good automation engine, less ecommerce-native

activecampaign.com

Strong for:

• complex journeys
• CRM-style automation
• lead nurturing

But for multiple Shopify-style stores, I’d generally pick an ecommerce-first tool.

My agency recommendation

For a small agency managing, say, 5–50 shops:

I’d probably standardize on Omnisend, build a library of reusable automations, and only move premium clients to Klaviyo when they need deeper analytics. Omnisend ventureharbour.com

A few questions would change the recommendation:

• How many shops are you managing (5, 20, 100+)?
• Are they mostly Shopify?
• Do clients pay for their own software accounts, or do you want one agency master account?

For a small agency managing, say, 5–50 shops:

For an agency managing multiple ecommerce shops on a tight budget, I’d shortlist Omnisend first, Klaviyo second.

My pick: Omnisend

Omnisend is particularly well suited to your setup because you can manage multiple stores from one account, switch between them, control team permissions, and copy templates/workflows/segments between stores. It supports up to 500 stores under one account. Each store is still billed separately, though, based on its own contact count. support.omnisend.com

The current pricing is also attractive for budget-conscious agencies:

• Free: 250 contacts / 500 emails per month
• Standard: starts at $16/mo, but SMS isn't available for new subscribers on this tier
• Pro: starts at $59/mo, with SMS available as an add-on starting around $0.007/SMS in the US/Canada. support.omnisend.com

That makes Omnisend my choice if you're managing lots of smaller Shopify/WooCommerce stores and don't need extremely sophisticated customer-data modeling.

When I'd choose Klaviyo instead

Klaviyo is better if your agency is doing sophisticated lifecycle marketing—complex segmentation, advanced flows, predictive analytics, and heavy Shopify customization.

It has good multi-account functionality: one login can switch between multiple client/store accounts. More importantly for an agency, Klaviyo has shared billing, where related accounts can potentially draw from one pooled email/SMS allowance. Klaviyo says this can support one parent plus up to 33 child accounts, although shared billing requires approval from Klaviyo Support. help.klaviyo.com

The catch is cost. Once client lists get large, Klaviyo can become substantially more expensive than Omnisend.

What I'd do for an agency

One important caveat: neither platform gives you one giant shared audience across unrelated client stores—and you generally don't want that anyway. Each client should have isolated customer data, sending domains, consent records, automations, etc. The useful "shared" layer is your agency's users, templates, processes, and account management.

If you tell me roughly how many shops you manage, average contacts per shop, whether they're Shopify/WooCommerce/etc., and approximate monthly email + SMS volume, I can work out which setup is likely to be cheapest—including Omnisend vs Klaviyo vs Brevo vs MailerLite.

If you’re an agency managing multiple ecommerce stores, I’d optimize for three things: multi-store management, reusable campaigns/flows, and low cost per store.

My shortlist

1. Omnisend — probably your best fit

I'd start here for a budget-conscious agency.

Omnisend is specifically designed for ecommerce and lets you manage multiple stores from one account, switch between them, and reuse templates/workflows across stores. It also combines email, SMS and push rather than requiring separate tools. Omnisend Omnisend Help Center

The big caveat is that each store has its own subscription, so you don't literally get one cheap subscription covering all your clients. Omnisend Help Center

Current pricing starts at $16/month for Standard and $59/month for Pro. For new subscribers, SMS requires Pro, with SMS pricing starting at $0.007/message in the US/Canada. Omnisend Help Center Omnisend Help Center

For an agency, the killer feature is build once, reuse across stores. You could create standardized flows such as:

• Welcome series
• Abandoned cart
• Browse abandonment
• Post-purchase
• Win-back
• VIP/customer loyalty
• SMS promotion
• Back-in-stock

Then clone/adapt them for each client.

omnisend.com

2. Klaviyo — better if clients have serious revenue

Klaviyo is what I'd use when a client's ecommerce operation is large enough that segmentation, attribution and sophisticated lifecycle marketing justify the additional cost.

It supports multiple accounts under one login, which is useful for an agency managing several brands. Klaviyo Help Center It also has a shared-billing/account-family feature that can pool email and SMS usage across related accounts, although you have to request it from Klaviyo and approval is case-by-case. One account family can have a parent plus up to 33 child accounts. Klaviyo Help Center

That could actually be very interesting for your agency if you have several related stores and enough combined volume.

Klaviyo's free tier currently covers up to 250 profiles and 500 emails/month, plus $5/month of mobile messages. Klaviyo

I'd therefore think of Klaviyo as your premium client tier, rather than putting every small client on it.

3. Mailchimp — only if SMS isn't central

Mailchimp can make sense for clients who mostly need newsletters, basic automations and straightforward campaigns.

But if your selling point to clients is "we manage your ecommerce email + SMS lifecycle marketing," I'd lean Omnisend or Klaviyo. Ecommerce-specific automation is where those platforms make more sense.

What I'd actually do as an agency

I'd create two service tiers:

Starter clients → Omnisend

Use standardized, agency-owned templates and flows. Keep the setup highly repeatable so you're not spending five hours rebuilding the same abandoned-cart sequence for every store.

Larger clients → Klaviyo

Use it when the client has enough traffic/revenue that advanced segmentation, predictive analytics, attribution and more sophisticated customer journeys can pay for themselves.

One particularly attractive setup is to investigate Klaviyo shared billing for clients that are sufficiently related; otherwise, Omnisend's multi-store setup is probably simpler operationally. Klaviyo Help Center

If I were starting your agency today on a tight budget, I'd pick Omnisend first. Its multi-store workflow/template reuse is unusually well aligned with an agency model, while the email + SMS combination keeps your tech stack small. Omnisend Omnisend Help Center

If you tell me roughly how many shops you manage, average contacts per shop, and whether they're mostly Shopify/WooCommerce/BigCommerce, I can work out which setup is likely to be cheapest and what I'd charge each client.

For an agency managing multiple ecommerce shops on a tight budget, I’d shortlist these:

1. Omnisend — my recommendation

Omnisend is unusually well suited to your situation. You can manage multiple stores from one account, switch between them, reuse templates/workflows, and control team access by store. Each store still has its own data and subscription, which is important for keeping client accounts separated. Omnisend Help Center Omnisend Help Center

More importantly for an agency, Omnisend added a Partner Portal and templated accounts in 2026. You can build a library of campaigns, automations and signup forms once, then copy them into client stores. Omnisend Help Center Omnisend Help Center

Its current Pro plan starts around $59/month list price, with unlimited email and SMS available as an add-on; the current pricing page is showing promotional pricing as well. Omnisend Help Center Omnisend

Why I'd choose it: you're paying for an ecommerce-focused platform rather than a general marketing platform, and the multi-store/template functionality directly attacks the biggest agency cost: repetitive setup.

2. Klaviyo — better if sophistication matters more than price

Klaviyo is probably the stronger choice if your clients need sophisticated segmentation, reporting, predictive analytics, and complex lifecycle marketing.

It supports multiple accounts under one login and has Portfolios for viewing/managing multiple brand accounts. Klaviyo Help Center Klaviyo Help Center

There's also a particularly interesting option for an agency: shared billing can pool email/SMS usage across related Klaviyo accounts. It's not automatically available—you have to request it from Klaviyo, and approval is case-by-case. Klaviyo Help Center

The downside is cost. For a budget-conscious agency with lots of small stores, I'd only move to Klaviyo when a client's revenue/complexity justifies it.

3. Sendlane — worth testing

I'd put Sendlane on the shortlist if you want something more agency-oriented than a basic email tool but don't need all of Klaviyo's sophistication.

That said, I wouldn't make it your default without pricing out your actual client portfolio. With 10–20+ stores, the multi-account economics matter much more than the headline monthly price.

What I'd do in your shoes

I'd standardize the agency around Omnisend and create a reusable "agency playbook":

• Welcome series
• Abandoned cart
• Browse abandonment
• Post-purchase
• Win-back
• Product replenishment
• VIP/customer segments
• Promotional campaign templates
• SMS opt-in + abandoned-cart SMS
• Basic reporting dashboard

Then use Omnisend's templated-account functionality to clone the proven setup into each new Shopify/WooCommerce/BigCommerce client. Omnisend Help Center

One important caveat: you don't actually get one shared subscription across all stores. Each Omnisend store has its own subscription and is billed according to its contact count. What you consolidate is the agency's management, users, templates, workflows and operational overhead. Omnisend Help Center

If you tell me roughly how many shops you manage (e.g. 5, 20, 50), average contacts per shop, and whether they're mostly Shopify, I can work out which setup is likely to be cheapest and compare the approximate monthly cost of Omnisend vs. Klaviyo for your agency.

Why I'd choose it: you're paying for an ecommerce-focused platform rather than a general marketing platform, and the multi-store/template functionality directly attacks the biggest agency cost: repetitive setup.

2. Klaviyo — better if sophistication matters more than price

Klaviyo is probably the stronger choice if your clients need sophisticated segmentation, reporting, predictive analytics, and complex lifecycle marketing.

It supports multiple accounts under one login and has Portfolios for viewing/managing multiple brand accounts. Klaviyo Help Center Klaviyo Help Center

There's also a particularly interesting option for an agency: shared billing can pool email/SMS usage across related Klaviyo accounts. It's not automatically available—you have to request it from Klaviyo, and approval is case-by-case. Klaviyo Help Center

The downside is cost. For a budget-conscious agency with lots of small stores, I'd only move to Klaviyo when a client's revenue/complexity justifies it.

3. Sendlane — worth testing

I'd put Sendlane on the shortlist if you want something more agency-oriented than a basic email tool but don't need all of Klaviyo's sophistication.

That said, I wouldn't make it your default without pricing out your actual client portfolio. With 10–20+ stores, the multi-account economics matter much more than the headline monthly price.

What I'd do in your shoes

I'd standardize the agency around Omnisend and create a reusable "agency playbook":

• Welcome series
• Abandoned cart
• Browse abandonment
• Post-purchase
• Win-back
• Product replenishment
• VIP/customer segments
• Promotional campaign templates
• SMS opt-in + abandoned-cart SMS
• Basic reporting dashboard

Then use Omnisend's templated-account functionality to clone the proven setup into each new Shopify/WooCommerce/BigCommerce client.

For an agency managing multiple ecommerce shops on a tight budget, I’d prioritize platforms that let you:

• manage multiple brands/workspaces cleanly
• reuse flows/templates
• keep client data separated
• avoid paying enterprise pricing per store
• handle both email + SMS in one place

My shortlist:

My recommendation for your situation

Default agency stack: Omnisend

• Create one agency account.
• Add each shop as its own store/workspace.
• Build reusable templates:
  • welcome series
  • abandoned cart
  • browse abandonment
  • post-purchase
  • winback
  • VIP/customer segments
• Charge clients a monthly management fee + platform pass-through.

It’s probably the best balance of cost, ecommerce features, and operational simplicity for many small shops. www.omnisend.comecommerce-times.com

When I’d use Klaviyo instead

Use Klaviyo per client if:

• the store is doing meaningful volume (e.g., six figures/month)
• segmentation matters heavily
• you need detailed attribution reporting
• you’re running sophisticated lifecycle marketing

Klaviyo tends to win once the client’s retention program is a major revenue channel. ecommerce-times.com

Agency workflow I’d avoid

I would avoid putting all clients into one shared customer database. Even if the software technically allows it, it creates problems with:

• customer data ownership
• unsubscribes
• reporting
• client offboarding
• compliance

Better model:

• agency owns the master login/admin relationship
• each client has a separate store/account
• you standardize templates and processes across them

A couple questions would change the recommendation:

1. Are these mostly Shopify, WooCommerce, BigCommerce, or mixed?
2. Roughly how many shops (5, 20, 100+)?
3. Do clients pay you for the software, or are you trying to absorb the cost into your retainer?

For an agency managing multiple ecommerce shops on a tight budget, I’d shortlist these:

1. Omnisend — my pick

This is probably where I'd start.

Omnisend explicitly supports multiple stores under one account, letting your team switch between stores without separate logins. You can also copy templates, workflows and segments between stores, while keeping each shop's customer data and reporting separate. It supports up to 500 stores under one account. support.omnisend.com

The important caveat for an agency: each store still has its own subscription, so you're not getting one magical unlimited agency license. But centralized users, billing, and management make it much less painful operationally. support.omnisend.comhelp.klaviyo.comhelp.klaviyo.com

Pricing is particularly attractive for small shops: Standard starts at $16/month, while Pro starts at $59/month and is the tier that currently includes SMS for newer subscriptions. SMS starts at $0.007/message according to Omnisend's current pricing information. support.omnisend.com

Why I'd choose it for an agency: you can build a master set of ecommerce flows—welcome, abandoned cart, browse abandonment, post-purchase, win-back, etc.—and replicate them across clients rather than rebuilding everything.

2. Klaviyo — best if clients can afford it

Klaviyo is the more sophisticated option, particularly if you're doing serious segmentation, predictive analytics and highly customized automation.

Its newer Portfolios feature is specifically designed for managing multiple brand accounts, including client brands for agencies, with a high-level view of performance, billing, users and data. Portfolios themselves don't add a fee. help.klaviyo.com

The downside for your situation is cost. You're paying for each client's Klaviyo account, and SMS is an additional usage-based cost. help.klaviyo.com

I'd use Klaviyo when the client's revenue justifies the extra sophistication, rather than making it your default platform for every small shop.

3. Sendlane — worth considering for volume

Sendlane is interesting if your agency eventually gets into larger sending volumes. Its pricing model is based on send volume rather than profiles, with unlimited contacts, and SMS starts at $0.009/credit including carrier fees. www.sendlane.com

But for a collection of small ecommerce stores, I'd generally favor Omnisend because its entry-level economics are much friendlier.

What I'd actually do

I'd standardize your agency around Omnisend and create a reusable "agency playbook":

• Core flows: welcome → abandoned cart → browse abandonment → post-purchase → win-back
• Reusable templates: 10–20 proven campaign designs
• Reusable segments: VIP, recent purchasers, engaged subscribers, lapsed customers
• SMS: reserve for high-value events rather than blasting every campaign
• Client separation: each store gets its own data, reporting and billing
• Agency account: your team gets centralized access and can move between clients

That gives you a fairly scalable setup without forcing a $500+/month marketing stack onto every tiny client.

One particularly useful feature is that Omnisend lets agencies keep separate client accounts while having the same agency users access them, and explicitly recommends that model for partners/agencies when clients need separate ownership and billing. support.omnisend.com

Bottom line:
Omnisend for most clients → Klaviyo when a client grows into it → Sendlane if your agency becomes particularly volume-heavy.

If you tell me roughly how many shops you manage, average subscriber count per shop, and whether they're Shopify/WooCommerce/etc., I can work out which setup would be cheapest and what the approximate monthly software cost would be.

For an agency managing multiple ecommerce stores on a tight budget, I’d shortlist these three:

1. Omnisend — my pick for an agency

This is probably where I'd start.

Omnisend explicitly supports multiple stores under one account, letting your team switch between stores without logging in/out. More importantly for an agency, you can reuse email templates and workflows across stores, which can eliminate a lot of repetitive setup. Email, SMS, and push are also handled in the same platform. www.omnisend.com

The big caveat: each store has its own subscription, so you don't literally get one cheap plan covering every client's contacts. support.omnisend.com

For current pricing, Omnisend's Standard plan starts around $11.20/month in the pricing interface for 500 contacts, while Pro is currently positioned as the plan that includes SMS for newer paid subscribers. SMS pricing starts at $0.007/message at high US volume. www.omnisend.com

Why I'd choose it: your agency can build a proven abandoned-cart/welcome/post-purchase/etc. framework once, then replicate it across clients.

2. Klaviyo — best if clients are more sophisticated

Klaviyo is the one I'd choose if you're managing higher-revenue stores where segmentation, attribution, automation and analytics matter more than software cost.

It supports multiple accounts under one login, and paid users can create portfolios to get a consolidated view across accounts. You can also clone flows, campaigns, segments and templates between accounts. help.klaviyo.com

There's an especially interesting option for an agency: Klaviyo has shared billing that can combine up to 20 accounts under one billing family, with a shared pool of email/SMS usage. However, you have to request it and approval is case-by-case. help.klaviyo.com

So I'd investigate that if you have, say, 5–15 stores and enough volume to negotiate.

Downside: it can get expensive quickly, and you're generally maintaining separate Klaviyo accounts for separate stores.

3. Brevo — best if cost is the overriding concern

Brevo is worth considering if you don't need the ecommerce-specific depth of Omnisend/Klaviyo.

Its current free plan includes 300 email sends/day, up to 100,000 contacts, and both email and SMS campaigns. Paid plans start at $9/month. help.brevo.com

I'd favor it for clients who need straightforward newsletters, promotional campaigns and SMS rather than elaborate ecommerce lifecycle automation.

What I'd do if I were running your agency

I'd standardize on Omnisend, unless your clients are already heavily invested in Klaviyo.

Build a reusable agency "master" system:

Core automations

• Welcome series
• Abandoned cart
• Browse abandonment
• Post-purchase
• Cross-sell
• Win-back
• Review request
• VIP/customer appreciation

Then create a master template library that you customize per client.

That matters more than saving another $5–10/month per account: if you can deploy a new client's email/SMS system in a couple of hours instead of 1–2 days, the agency economics become much better.

One thing I'd want to know before making the final recommendation

If you tell me roughly:

1. Number of stores: e.g. 5, 10, 25
2. Average contacts/store: e.g. 2,000
3. Shopify/WooCommerce/etc.
4. Approximate monthly email sends/store
5. Whether clients pay the software bill or you do

…I can work out which platform would actually be cheapest for your agency, including the multi-store/billing implications, rather than just comparing headline prices.

For an agency managing multiple ecommerce shops on a tight budget, I’d shortlist these three:

1. Omnisend — my pick for you

This is probably where I'd start.

Omnisend is specifically built around ecommerce and lets you manage multiple stores from one account, with separate data, automations, reporting and permissions for each store. More importantly for an agency, you can reuse templates and workflows across stores rather than rebuilding everything. support.omnisend.comwww.omnisend.com

The catch: each store has its own subscription, so don't expect one cheap account to cover unlimited clients. support.omnisend.com

Current pricing is attractive: Standard starts at $16/month, while Pro starts at $59/month and adds SMS; current SMS pricing starts at $0.007/message for high-volume US/Canada sending. support.omnisend.com

Why I'd choose it: you get the ecommerce-specific flows you actually need—welcome, abandoned cart, browse abandonment, post-purchase, winback, etc.—without paying Klaviyo-level prices.

One important 2026 change: for new subscribers after May 4, 2026, SMS requires Pro, so factor that into your per-client cost. support.omnisend.com

2. Klaviyo — best if clients can afford it

Klaviyo is still the stronger choice if you're doing sophisticated segmentation, personalization and reporting.

It's also become quite agency-friendly. One login can access multiple client accounts, and Klaviyo Portfolio gives you centralized performance, billing and user management. You can even clone campaigns, forms, segments and templates across accounts. help.klaviyo.com

For an agency specifically, bulk user management across client accounts is a big operational advantage. help.klaviyo.com

The downside is simply cost. Klaviyo bills each account based on its profiles/email and separately for mobile messaging, so having 10–20 small clients can get expensive quickly. help.klaviyo.com

There's also a potentially interesting option for larger client groups: Klaviyo offers shared billing for up to 20 accounts, subject to approval. help.klaviyo.com

I'd use Klaviyo when: the client has enough revenue that better segmentation/analytics can justify the extra software cost.

3. Brevo — best ultra-budget option

Brevo is worth considering if your clients have small lists and relatively simple requirements.

Its free plan includes 300 emails/day, up to 100,000 stored contacts, and both email and SMS campaigns. Starter starts at $9/month. help.brevo.com

The problem is that it's less purpose-built for ecommerce than Omnisend/Klaviyo. If you're managing Shopify/WooCommerce stores and want a standardized library of ecommerce automations, I'd rather have Omnisend.

What I'd do if I were your agency

I'd actually standardize on two tiers:

Small/low-revenue clients → Omnisend
Larger/high-value clients → Klaviyo

Then build a common agency playbook:

1. Welcome series
2. Abandoned cart
3. Browse abandonment
4. Post-purchase
5. Cross-sell
6. Winback
7. VIP/customer segment
8. Promotional email/SMS campaigns

Build the templates/flows once, then adapt the branding, products and offers for each store.

Omnisend is particularly compelling for this model because it explicitly supports sharing templates/workflows between stores. support.omnisend.comwww.omnisend.com

If you're talking about 5–50+ Shopify stores, I can also compare the actual monthly cost per store at 1k / 5k / 10k contacts, including SMS, and tell you which setup will be cheapest for an agency.

For an agency managing multiple ecommerce shops on a tight budget, I’d shortlist these:

1. Omnisend — my first choice

This is probably the best fit for your situation.

• Built specifically for ecommerce rather than generic email marketing.
• Supports multiple stores, with easy switching between them.
• You can create templates/workflows once and reuse them across stores. www.omnisend.com
• Email, SMS, and push are handled in the same platform.
• Pricing is generally considerably lower than Klaviyo, especially as lists grow. Omnisend currently starts around $16/month for its paid tier. www.omnisend.com
• Particularly attractive if your clients are smaller Shopify/WooCommerce brands and don't need sophisticated CDP-level analytics.

Agency advantage: you can standardize your agency's lifecycle framework—welcome, abandoned cart, browse abandonment, post-purchase, winback, etc.—then adapt the branding/content for each shop rather than rebuilding everything.

2. Klaviyo — best if your clients are bigger

I'd use Klaviyo when a client's revenue/list size justifies it.

Its big advantage is data depth: sophisticated segmentation, behavioral targeting, predictive analytics, and very deep ecommerce integrations. The downside for a budget-conscious agency is that pricing scales substantially with contacts. For example, current published pricing puts 50K contacts at roughly $720/month for email alone, before meaningful SMS usage. www.omnisend.com

So I'd avoid putting every tiny client on Klaviyo just because it's the industry standard.

3. Drip — worth considering for email-heavy clients

Drip is a solid ecommerce automation platform, but I'd put it behind Omnisend if SMS is an important part of your service. Your use case favors having email + SMS + ecommerce functionality together rather than assembling multiple tools.

What I'd do if I were running the agency

I'd actually use a two-tier stack:

The important thing is not to force every client into the same platform. Your agency can standardize the strategy, templates, flows, reporting and processes while letting the underlying ESP vary.

For your specific requirement—multiple shops + shared campaign assets + email/SMS + tight budget—Omnisend is the one I'd test first. Its multi-store functionality is unusually relevant to an agency: templates and workflows can be reused across stores, and you can switch between stores without repeatedly logging in. www.omnisend.com

If you tell me roughly how many shops you manage, average contacts per shop, and whether they're mostly Shopify/WooCommerce, I can work out which setup would likely be cheapest—including the difference between giving each client their own account vs. managing everything through an agency account.

If you’re an agency managing multiple ecommerce shops on a tight budget, I’d optimize for low cost per client + easy account separation + solid Shopify/WooCommerce integrations + email/SMS automation, rather than picking the most powerful enterprise platform.

My shortlist

1. Omnisend — my first choice

For an agency specifically focused on online shops, I'd start here. It's ecommerce-native, combines email + SMS + automation, and is generally cheaper than Klaviyo at comparable contact counts. Current comparisons show Omnisend particularly pulling ahead as lists get larger. www.omnisend.com

The big advantage for you is that you don't need to sacrifice ecommerce functionality just to keep costs down: abandoned-cart, post-purchase, segmentation, product-oriented campaigns and multichannel workflows are central to the product.

Omnisend pricing

I'd use this when: most of your clients are Shopify/WooCommerce stores and you want one standardized system your team can learn.

2. Brevo — best if the budget is really tight

Brevo is particularly interesting for an agency because its email pricing is primarily send-volume based rather than active-contact based. That can be dramatically cheaper when clients have large databases but don't send constantly. Its platform also combines email, SMS, CRM and automation. www.omnisend.com

For example, its current entry pricing starts around $9/month for 5,000 emails, while the free tier supports a very large contact database but limits daily sending. www.omnisend.com

Brevo pricing

I'd use this when: you have lots of smaller clients and want to minimize your software overhead.

3. Klaviyo — don't make it your default for every client

Klaviyo is arguably the strongest choice when a store has sophisticated segmentation, lots of behavioral data and significant revenue flowing through email/SMS. But its pricing scales with active profiles, and SMS is an additional cost. www.omnisend.com

That makes it harder to justify across 10, 20, or 50 small client accounts.

I'd reserve Klaviyo for clients where the additional revenue generated by its deeper analytics/automation clearly outweighs the extra subscription cost.

Klaviyo pricing

What I'd actually do as an agency

I'd standardize around two tiers:

Small/low-volume clients → Brevo
Cheap, straightforward, shared agency processes, email + SMS without paying a premium for ecommerce sophistication.

Serious ecommerce clients → Omnisend
More ecommerce-specific automation and better fit for stores where lifecycle marketing is a meaningful revenue channel.

Then upgrade exceptional clients to Klaviyo only when their size/complexity justifies it.

One important consideration: don't assume "one master account for all shops" is the cheapest architecture. You generally want each client's store/customer database logically isolated, while your agency has centralized access/management. Otherwise permissions, billing, unsubscribe compliance, reporting and client offboarding can become painful.

If you tell me roughly how many shops you manage (e.g. 10/30/100), average contacts per shop, and whether they're mostly Shopify, I can work out which setup is likely to be cheapest and give you an estimated monthly agency software bill.

For an agency managing multiple ecommerce shops on a tight budget, I’d shortlist these:

🥇 My pick: Omnisend

I'd start with Omnisend, particularly if most of your clients are Shopify/WooCommerce/BigCommerce stores.

The big advantage for an agency is that Omnisend was designed around multiple stores: you can switch between stores from one account, give different team members store-specific permissions, and reuse campaigns/workflows across stores. www.omnisend.comsupport.omnisend.com

Even better, their Partner Portal has templated accounts: you can build automations, campaigns and signup forms once and copy them into client stores. That's extremely useful if you're repeatedly setting up abandoned-cart, welcome, post-purchase, win-back, etc. support.omnisend.comwww.omnisend.com

The catch is important: each store still has its own subscription, so Omnisend doesn't magically consolidate all your clients into one cheap bill. www.omnisend.comsupport.omnisend.com

For new subscriptions, SMS is currently on the Pro plan, with US SMS pricing starting at $0.007/message at high volume. support.omnisend.com

💰 Brevo if minimizing software spend is priority #1

Brevo is worth serious consideration if your clients have relatively small lists or don't need sophisticated ecommerce segmentation.

Its free plan includes email and SMS campaigns, and paid plans start at $9/month. help.brevo.com

It also has an explicit agency model, letting you switch between client accounts from your agency account and manage clients centrally. www.brevo.com

I'd choose Brevo when the agency's priority is "get 10–20 small shops running campaigns cheaply" rather than maximizing ecommerce automation.

🧠 Klaviyo if your clients can afford it

Klaviyo is the one I'd use for higher-value stores where sophisticated segmentation, attribution and automation justify the cost.

It supports multiple accounts under one login, and agencies can use portfolios to oversee multiple accounts. help.klaviyo.com There is also a shared-billing program that can link up to 20 accounts and pool email/SMS usage, although approval is case-by-case. help.klaviyo.com

That's potentially very interesting for an agency—but I wouldn't make Klaviyo the default for budget clients.

What I'd actually do in your shoes

I'd use a two-tier agency stack:

Small/budget clients → Omnisend or Brevo
Larger/revenue-focused clients → Klaviyo

And standardize your agency around a reusable library of:

• Welcome series
• Abandoned cart
• Browse abandonment
• Post-purchase
• Cross-sell
• Win-back
• VIP/customer segmentation
• Promotional email/SMS templates
• Holiday campaign templates

If your shops are mostly Shopify, I'd lean Omnisend. Its multi-store + reusable-template workflow is unusually well suited to an agency model. support.omnisend.comwww.omnisend.com

If you tell me roughly how many shops you manage, average subscriber count per shop, and whether they're Shopify/WooCommerce/etc., I can work out which platform would be cheapest at your actual scale and how I'd structure the accounts.

For an agency managing multiple ecommerce stores on a tight budget, I’d shortlist these three:

1. Omnisend — best budget/value choice

This would be my first choice if the stores are primarily Shopify/WooCommerce-style ecommerce businesses.

• Built specifically around ecommerce email + SMS.
• Current Standard pricing starts at $16/month (with a temporary 30% introductory discount shown currently), while Pro starts at $59/month. support.omnisend.comwww.omnisend.com
• Pro includes unlimited email and SMS is available as a volume-priced add-on, currently starting at $0.007/SMS for high-volume U.S. sends. support.omnisend.comwww.omnisend.com
• Strong automations for abandoned cart, welcome, post-purchase, winback, etc.
• They explicitly support ecommerce agencies/partners. support.omnisend.com
• Free migration of lists, segments, flows and templates is a nice bonus when consolidating stores. support.omnisend.comwww.omnisend.com

The catch: their new pricing makes SMS Pro-only for customers subscribing from May 4, 2026 onward. support.omnisend.com

2. Klaviyo — best if you want a serious agency platform

I'd pick this if your agency expects to grow and clients are willing to pay more for sophisticated segmentation, analytics and automation.

Klaviyo is particularly interesting for your use case now because it has multi-account/portfolio functionality. A single login can access multiple client/store accounts, and portfolios provide consolidated performance, billing and account visibility. help.klaviyo.com

It also has newer organization-level administration and agency-oriented tooling. help.klaviyo.com

Big downside: cost. If you're managing a lot of small stores, separate Klaviyo accounts can become expensive relative to the revenue you're generating for each client.

3. Brevo — best ultra-low-cost/generalist option

Brevo is worth considering if price is the overriding concern.

Its free plan includes email and SMS campaigns, with 300 email sends/day, and paid plans start at $9/month. help.brevo.com

It also has an agency partner setup where you can switch between client accounts and let your colleagues access/manage those accounts. help.brevo.com

The major caveat is that Brevo's centralized sub-organization management is an Enterprise feature, so you don't get the full agency-control experience cheaply. help.brevo.com

What I'd do in your position

The important architectural point: I wouldn't put all your clients' customers into one giant shared marketing database. I'd generally keep one account/workspace per store, but give your agency team centralized access and standardized templates, flows, naming conventions and reporting.

That gives you client isolation while still allowing your team to operate efficiently.

If you're managing, say, 10–50 Shopify stores, I can also compare the actual monthly agency cost of Omnisend vs Klaviyo vs Brevo at different store/customer counts—that's probably the most useful next step for a tight-budget agency.

For an agency managing multiple ecommerce stores on a tight budget, I’d shortlist these three:

My pick: Omnisend

For your particular situation, I'd start with Omnisend.

It lets you connect multiple stores under one account and switch between them without separate logins. More importantly for an agency, you can create an email template or automation once and reuse it across stores. It supports email, SMS and push in the same platform. support.omnisend.com

The current pricing is also unusually attractive for smaller shops: Standard starts at $16/month, while Pro starts at $59/month and adds SMS; current SMS pricing starts around $0.007/message for US/Canada at the applicable volume tier. support.omnisend.com

The catch: each store still has its own subscription, so you don't get one giant shared pool of contacts/billing across all clients. support.omnisend.com

Brevo is worth considering if cost is the #1 priority

Brevo is particularly interesting for an agency because its agency program provides centralized multi-account management, so you can switch between client accounts from one place. www.brevo.com

Pricing starts at $9/month, with email + SMS available, although SMS is charged separately. help.brevo.com

I'd choose Brevo if your stores are relatively simple and you're trying to minimize software costs. I'd choose Omnisend if ecommerce-specific automations—abandoned cart, post-purchase, product recommendations, browse abandonment, etc.—are central to what you're selling clients.

Klaviyo if clients can afford it

Klaviyo is probably the strongest choice if you're managing more sophisticated ecommerce programs and want excellent segmentation, analytics and automation.

It supports multiple accounts under one login, and Klaviyo has a shared-billing program allowing up to 20 accounts (one parent + 19 children), although approval is case-by-case. help.klaviyo.com

However, I wouldn't make it the default for a tight-budget agency. Klaviyo also changed its mobile messaging pricing to per-message dollar rates in July 2026, so SMS costs need to be modeled carefully for each client. help.klaviyo.com

What I'd actually do

If you have, say, 10–30 Shopify stores, I'd structure it like this:

Agency standard → Omnisend

• One agency login
• One store/account per client
• Standardized welcome flow
• Abandoned-cart flow
• Browse abandonment
• Post-purchase flow
• Win-back flow
• Standard campaign templates
• Reusable agency-built templates/workflows
• Client-specific branding and segments

Then move only your larger/more sophisticated clients to Klaviyo if they need its deeper capabilities.

One important distinction: if by "shared ecommerce email and SMS" you mean one central platform where your agency can pool contacts/billing across all clients, rather than simply managing multiple separate store accounts from one dashboard, that's a different requirement. I can compare the economics of that setup specifically—including what it would cost for, say, 10 stores × 5,000 contacts each.

For an agency managing multiple ecommerce stores on a tight budget, I’d prioritize one platform per client/store, strong ecommerce integrations, reusable flow templates, and predictable SMS costs rather than trying to force every client into the most sophisticated platform.

My shortlist

1. Omnisend — my default recommendation

I'd probably standardize your agency around Omnisend unless a client has a reason to need something more advanced.

It's specifically ecommerce-focused and combines email, SMS, automation, segmentation and web push. The current paid plans start at $16/month for Standard, while Pro starts at $59/month; importantly, for new subscribers since May 4, 2026, SMS is on Pro with usage-based pricing starting at $0.007/SMS in the US/Canada. support.omnisend.com

That makes it particularly attractive when you're managing lots of smaller stores: you're not paying Klaviyo-level prices simply to have abandoned-cart, welcome, post-purchase and winback flows.

I'd use it for: Shopify/WooCommerce stores doing roughly $0–5M/year where your agency wants a repeatable setup.

2. Klaviyo — keep it for your bigger clients

Klaviyo is still the one I'd choose when the client has substantial customer data and you're doing sophisticated segmentation, attribution, predictive analytics, etc.

The catch for a budget-conscious agency is cost. For example, current pricing cited for 10,000 contacts is around $150/month for email and $165/month with SMS, versus Omnisend's substantially lower-cost positioning. www.omnisend.com

So I wouldn't make Klaviyo your universal agency standard unless your clients' revenue justifies it.

3. Brevo — worth considering for tiny clients

Brevo is interesting if your priority is keeping the absolute software bill down and the stores don't require extremely sophisticated ecommerce segmentation.

I'd put it behind Omnisend for a serious DTC operation, though. Omnisend's ecommerce-specific workflows make it easier to standardize an agency's implementation.

What I'd actually do as an agency

I'd create two tiers:

Agency Standard → Omnisend

• Smaller/mid-market ecommerce clients
• Email + SMS
• Welcome flow
• Abandoned cart
• Browse abandonment
• Post-purchase
• Winback
• Promotional campaigns
• Basic segmentation
• Reusable agency templates

Agency Premium → Klaviyo

• Larger stores
• Complex product/customer data
• Advanced segmentation
• Predictive analytics
• Sophisticated attribution
• Clients where an extra $100–500+/month is insignificant relative to revenue

That gives your team one inexpensive operating system for most accounts, while avoiding the mistake of putting every client on the same expensive platform.

One other important point: don't try to put all your clients into one shared sending account. Keep each brand's audiences, domains, consent records, analytics and sending reputation separated. What you want to share is your agency's templates, SOPs, flow architecture and reporting process, not the customer databases.

If you tell me roughly how many stores you manage, average contacts/store, Shopify vs WooCommerce, and approximate monthly SMS volume, I can run the numbers and recommend the cheapest setup across 10/25/50+ client stores.

For an agency managing multiple ecommerce stores on a tight budget, I’d prioritize platforms that let you centralize access, reuse campaigns/flows, and keep each client’s data separated.

My shortlist

I'd start with Omnisend. It is unusually well suited to an agency: one account can manage multiple stores, you can switch between stores, assign permissions by store, and—importantly—you can create reusable campaign/automation templates and copy them across client stores. support.omnisend.com

The catch is that each store still has its own subscription, so it isn't one cheap account that magically covers all your clients. support.omnisend.comsupport.omnisend.com

Omnisend's current pricing is attractive for smaller shops: Standard starts at $16/month, while Pro starts at $59/month and is the plan that supports SMS for new subscribers, with SMS starting at $0.007/message in the US/Canada at qualifying volume. support.omnisend.com

Where Brevo gets interesting

Brevo is worth considering if your clients have relatively modest sending volumes but large contact databases. Its free plan currently allows 100,000 stored contacts and 300 email sends/day, and includes both email and SMS campaigns. Paid plans start at $9/month. help.brevo.com

The downside for an ecommerce agency is that I would generally favor Omnisend's ecommerce-oriented workflows, store management, and reusable templates over Brevo if Shopify/ecommerce automation is the core of your service.

When I'd pay for Klaviyo

I'd use Klaviyo when a client's revenue justifies more sophisticated segmentation, predictive analytics, attribution, and lifecycle marketing. It's excellent, but if you're managing 10–20 smaller shops, putting every client on Klaviyo can become unnecessarily expensive.

What I'd do as an agency

I'd build an Omnisend agency template library:

• Welcome series
• Abandoned cart
• Browse abandonment
• Post-purchase
• Cross-sell
• Win-back
• Review request
• VIP/customer segmentation
• Promotional email + SMS templates
• Holiday/Black Friday campaigns

Then customize branding, products, offers, and segmentation for each shop. Omnisend specifically supports agency partner templates that can be copied into client stores, which could save a substantial amount of production time. support.omnisend.comsupport.omnisend.com

Bottom line:
Omnisend = my recommendation for your agency.
Brevo = investigate if minimizing software spend is the absolute priority.
Klaviyo = reserve for higher-revenue clients where advanced lifecycle marketing can pay for itself.

If you tell me roughly how many stores you manage, average contacts/store, monthly email volume, and whether they're mostly Shopify, I can work out which setup would likely be cheapest and what I'd charge clients for it.