Answers that name a competitor

If you mean email marketing campaigns for multiple clients—newsletters, automations, campaign analytics, etc.—I’d look first at campaignmonitor.com.

It’s specifically designed around the problem you described:

• One agency login for multiple client accounts, rather than logging in/out constantly.
• Separate client accounts keep each client’s subscribers, campaigns, templates, and analytics isolated.
• Centralized account management and reporting, with the ability to quickly jump to client performance metrics.
• Role-based permissions so clients/team members only get the access they need.
• White-label/private-label options if you want the client-facing experience to look like your agency.
• Client-specific billing is supported too. Campaign Monitor

Another strong option: MailerLite

mailerlite.com is particularly appealing if your priority is simply eliminating the login/logout headache. It lets you switch between separate client accounts in two clicks from one login, while keeping each client's subscribers, campaigns, automations, and templates separate. MailerLite

The catch is that MailerLite doesn't provide built-in white-label agency reporting; cross-client reporting requires using its API or another reporting layer. MailerLite

My pick

If you're managing Klaviyo, Mailchimp, HubSpot, etc. accounts that already belong to your clients, rather than choosing a new email platform, that's a different problem—the best tool is usually an agency management/reporting layer that connects to those existing accounts.

If you manage email campaigns for multiple client accounts and want to stop logging in and out, look for an agency-focused email marketing platform with:

• multi-client workspaces/sub-accounts
• role-based access
• consolidated reporting
• automated client reports
• template reuse
• optional white-label dashboards

Good options:

For a typical agency setup, I’d choose based on client count:

• 1–10 clients: MailerLite or Zoho Campaigns
• 10–50+ clients: Campaign Monitor or an agency-oriented platform with sub-accounts
• Need branded client reports: pair an email platform with a reporting dashboard tool
• Need one “command center” for all marketing channels: use a reporting platform on top of your email tools

A common stack is:

1. Email execution: Campaign Monitor / MailerLite / Zoho Campaigns
2. Reporting layer: AgencyAnalytics / Zoho Analytics
3. Client portal: white-labeled dashboard or scheduled reports

If you tell me roughly how many client accounts you manage (5, 20, 100+) and whether you need email sending only or email + ads/social/SEO reporting, I can narrow it down.

If you’re an agency managing multiple clients’ newsletters + automated email journeys + client-facing performance reporting, I’d narrow the field to five platforms rather than looking at generic email tools.

My shortlist

1. HighLevel — best overall for an agency

If your goal is “one place where my agency can run every client's marketing”, this is probably where I'd start.

It gives you client/sub-account separation, email, SMS, CRM, forms, funnels, workflows, reporting and white-label capabilities in one ecosystem. Recent agency-focused comparisons consistently put it at or near the top for this exact use case. tooldecisionengine.com

Choose it if: you're selling an ongoing marketing service rather than merely sending newsletters.

Downside: its email/newsletter experience isn't as refined as the best email-specialist platforms.

HighLevel

2. ActiveCampaign — best if email automation is the core service

This would be my choice if your agency does things like:

• Welcome sequences
• Lead nurturing
• Re-engagement
• Behavioral automations
• Lead scoring
• CRM-triggered campaigns
• Complex segmentation

Its automation capabilities are still one of its biggest advantages, and it has an agency/reseller ecosystem. www.emailtooltester.comwww.campaignmonitor.com

The important caveat: reporting/client dashboards aren't its strongest agency feature. A common agency stack is ActiveCampaign + a dedicated reporting platform such as AgencyAnalytics. ActiveCampaign specifically integrates with AgencyAnalytics for automated, white-labeled client dashboards. www.activecampaign.com

ActiveCampaign

3. Campaign Monitor — best if you're essentially an outsourced email department

This is particularly interesting if your workflow is:

Client A → newsletter + automations + reporting
Client B → newsletter + automations + reporting
Client C → newsletter + automations + reporting
...repeat 20 times.

Campaign Monitor has been specifically designed around agency/multi-client use, with centralized client management, white-label reporting and template controls. www.campaignmonitor.com

I'd favor this over HighLevel if your clients don't need CRM, funnels, SMS, lead pipelines, etc.

Campaign Monitor

4. Klaviyo — best for ecommerce

If most of your clients are Shopify/ecommerce brands, I'd stop looking and evaluate Klaviyo first.

Its strength is connecting email to actual customer/ecommerce behavior:

Viewed product → abandoned cart → purchased → repeat purchase → VIP → win-back, etc.

It also has excellent revenue attribution and segmentation. The tradeoff is that it's less of a generic agency operating system than HighLevel. www.emailtooltester.comtooldecisionengine.com

Klaviyo

5. Brevo — best value

I'd look at Brevo if you're managing lots of smaller clients where margins matter.

It combines email, automation, SMS and CRM features at relatively accessible pricing. The big caveat is that its true white-label capabilities are more restricted than some agency-oriented alternatives. www.emailtooltester.comtooldecisionengine.com

Brevo

What I'd actually build

For a typical 5–30 client marketing agency, I'd consider two architectures:

Option A — simplest

HighLevel → newsletters + automations + CRM + client accounts + reporting

Best if you want to consolidate your stack.

Option B — best email/reporting combination

ActiveCampaign → email + automation
AgencyAnalytics → client dashboards + cross-channel reporting

AgencyAnalytics can pull ActiveCampaign metrics into white-labeled dashboards alongside things like SEO, PPC and social data, which is particularly useful if email is only one component of your agency's monthly reporting. www.activecampaign.com

One important distinction

If by “centralize” you mean “I want my team to log into one system, switch between 20 client accounts, send campaigns, manage automations, and give each client their own dashboard”, I'd prioritize HighLevel or Campaign Monitor.

If you mean “I want the absolute best email automation engine and don't mind having a separate reporting layer”, I'd choose ActiveCampaign + AgencyAnalytics.

If you tell me roughly how many clients you manage, whether they're mostly B2B/local businesses/ecommerce, and whether clients need to log in themselves, I can narrow this to the best 2–3 options and compare their actual agency pricing/cost at your scale.

For an agency managing multiple clients’ newsletters, email automations, and performance dashboards, the best setup is usually not one tool but a small stack:

1. Email execution platform (campaigns + automations)
2. Client reporting/dashboard layer (white-labeled performance views)
3. CRM/data connectors (optional, depending on clients)

Here are the strongest options by agency type:

Best dashboard/reporting companions

For client-facing dashboards, I would usually pair the email tool with:

• AgencyAnalytics — best if you need branded client portals combining email, SEO, PPC, social, and analytics data. Zite
• Databox — better for KPI dashboards and executive-style reporting. AgencyPro
• Looker Studio — good low-cost option if your team is comfortable building dashboards manually.

My shortlist by agency model

If you run a marketing agency with 10–100 clients

Recommended stack:

• HighLevel for client accounts + automations
• AgencyAnalytics for reporting

Good fit if you sell “marketing systems” rather than just newsletters. Tool Decision Engine

If you run an email retention/newsletter agency

Recommended stack:

• Campaign Monitor or ActiveCampaign
• AgencyAnalytics or Databox

Good fit for recurring newsletters, nurture sequences, lead magnets, and lifecycle campaigns. Campaign Monitor Zite

If most clients are Shopify/ecommerce brands

Recommended stack:

• Klaviyo
• Databox or AgencyAnalytics

Klaviyo’s strength is revenue-driven flows (welcome, abandoned cart, post-purchase, win-back). The Open Rate Club

If clients need a simple “see everything” portal

Look for:

• white-label dashboards
• separate client workspaces
• scheduled reports
• permissions
• automated monthly summaries

A practical agency stack I’d choose

For a small-to-mid agency:

Client operations
→ HighLevel

Advanced email automation
→ ActiveCampaign (for complex clients) or Klaviyo (for ecommerce)

Reporting
→ AgencyAnalytics

Internal workflow
→ ClickUp or Asana

That gives you:

• one place to manage clients
• repeatable automation templates
• branded dashboards
• less manual reporting

If you tell me your agency type (B2B, ecommerce, local businesses, creators, SaaS, etc.) and approximate client count, I can narrow this to a 2–3 tool stack.

Reporting
→ AgencyAnalytics

Internal workflow
→ ClickUp or Asana

That gives you:

Yes. There are platforms that get pretty close to exactly that model—one agency account, multiple client environments, client-specific brand templates, permissions, and billing.

Best fits

• Marq — probably the strongest fit if the core need is branded templates + permissions. It supports brand-template libraries, locked design elements, custom roles, groups, and permissions at the brand/team/user level. Its enterprise plan also includes custom roles, group management, approvals, and template governance. Marq Marq Marq

marq.com

Caveat: Marq's billing model is primarily based on licenses within an account, so it isn't necessarily designed around agency → Client A pays X, Client B pays Y as separate billing entities. Marq

• Ploy — interesting if you're managing websites/sites for clients. It explicitly supports organizations + separate client workspaces, and lets you choose whether the agency owns billing or each client pays independently. You can also mix the two models. Ploy Support Docs

ploy.ai

• Orshot — very agency-oriented if you're talking about automated visual content/templates. It provides one isolated workspace per client, with separate templates, brand assets, API keys and render logs, plus white-labeling and partner pricing. Orshot

orshot.com

If you're describing a product you want to build

The model you're describing is essentially:

Agency
→ Client A workspace
→ Client B workspace
→ Client C workspace

Each workspace has:

• Its own brand kit
• Its own template library
• Its own users/roles
• Its own approval rules
• Its own assets
• Its own usage limits
• Its own billing/subscription
• Optional white-label/client portal

And the agency gets a master admin view across all clients.

That's actually a pretty compelling multi-tenant SaaS/agency platform architecture. The distinction I'd pay attention to is whether you want the agency to resell the software under its own pricing or simply manage separate client subscriptions. Platforms like Ploy explicitly support the former-ish agency billing structure, while Marq is stronger on the actual brand/template governance side. Ploy Support Docs Marq Help Center

If you tell me what kind of templates you're talking about (social posts, ads, presentations, websites, email, documents, AI prompts, etc.), I can narrow this down to the 3–5 platforms that most closely match your exact use case.

If you need white-label reporting + custom client-facing dashboards specifically for email performance, I’d shortlist platforms that can either ingest email metrics directly (ESP integrations/API) or combine email data with broader marketing analytics.

Best overall options

My recommendations by use case

1. Marketing agency reporting to clients

Choose AgencyAnalytics.

Good fit if clients need:

• Open rate
• Click-through rate
• Conversion metrics
• Campaign trends
• Revenue attribution
• Cross-channel reporting

It is designed around agency workflows: client dashboards, scheduled reports, branding, and client access. AgencyAnalytics AgencyAnalytics

2. You want a “software product” experience under your own brand

Choose ClicData, Zoho Analytics, or Klipfolio.

These are better when you want:

• Your own domain (e.g., reports.yourcompany.com)
• Your logo/colors
• Client login portals
• Custom KPI layouts
• Multiple client accounts with different permissions

ClicData and Zoho Analytics specifically emphasize white-label dashboards and client-facing branding. ClicData Zoho

3. You need advanced email-specific dashboards

Consider building on a BI layer:

Common email KPIs to expose:

• Deliverability rate
• Bounce rate
• Open rate (where available)
• Click rate
• Click-to-open rate
• Unsubscribe rate
• Spam complaints
• Revenue per campaign
• List growth
• Segment performance
• A/B test winners

A typical architecture:

1. Email platform (e.g., Klaviyo, Mailchimp, HubSpot, or another ESP)
2. Data connector/API
3. Dashboard layer (AgencyAnalytics, Zoho Analytics, ClicData, Klipfolio)
4. Branded client portal

My pick

• Agency with many clients: AgencyAnalytics
• Agency wanting a premium branded portal: ClicData or Zoho Analytics
• SaaS/company building a proprietary reporting product: Klipfolio or ClicData
• Email-only reporting product: build a custom dashboard layer around your ESP APIs

If you tell me which email platform you use (Klaviyo, Mailchimp, HubSpot, Salesforce Marketing Cloud, Iterable, etc.) and whether this is for an agency or internal client reporting, I can narrow it down.

If you mean one agency interface where your team can manage email + SMS for multiple ecommerce clients, I’d narrow it to Klaviyo vs. GoHighLevel, with the winner depending on what you’re optimizing for.

My pick for an ecommerce-focused agency: Klaviyo

Klaviyo is probably the best fit if your clients are primarily Shopify/DTC brands.

• Email + SMS in the same ecosystem
• Excellent ecommerce integrations and customer data
• Very strong segmentation, flows, attribution, and reporting
• You can connect multiple Klaviyo accounts to the same login and switch between them without logging in/out. Klaviyo Help Center
• Built specifically around ecommerce rather than being a generic agency CRM
• There is an official Klaviyo partner ecosystem for agencies. Klaviyo

The downside: you're still essentially managing separate client accounts, rather than having one giant shared workspace. For a retention/email-SMS agency, though, that's generally the right architecture.

My pick for a broader marketing agency: GoHighLevel

GoHighLevel is better if you want one agency operating system rather than primarily an ecommerce retention platform.

You get:

• Multiple client sub-accounts
• Email + SMS
• CRM
• Automations
• Funnels/websites
• Lead management
• White-labeling
• Agency-level management

That's where HighLevel has a major advantage: it was designed around the agency → multiple clients → sub-account model. Ecommerce Paradise

The tradeoff is that its ecommerce email/SMS functionality isn't as deep as Klaviyo's. For sophisticated Shopify segmentation, behavioral flows, and revenue attribution, Klaviyo is generally the stronger choice.

What about Omnisend?

Omnisend is worth considering if your agency has lots of smaller/mid-sized stores and you care about keeping costs and implementation complexity down.

It's ecommerce-native and combines email, SMS, and push. Its current offering also supports switching between multiple stores from one account, with support for up to 500 stores. Omnisend

The simple decision

If I were building an agency today specifically around email + SMS for ecommerce clients, I'd choose Klaviyo. The fact that you can access multiple client accounts from one login makes the multi-client workflow considerably easier, while retaining the ecommerce-specific data and automation depth. Klaviyo Help Center

If you tell me roughly how many clients you manage (e.g. 10, 50, 200+) and whether they're mostly Shopify, I can also compare Klaviyo vs GoHighLevel vs Omnisend specifically from an agency-owner perspective—including client management, pricing/margins, white-labeling, permissions, templates, reporting, and how easy it is to clone campaigns/flows across clients.

For an agency managing multiple ecommerce clients and needing email + SMS from one interface, the best choice depends on whether you prioritize ecommerce revenue performance or agency operations/white-label management.

Best overall options

My recommendation by agency type

If you are a Klaviyo/email retention agency

Choose Klaviyo.

Best when your service is:

• abandoned cart flows
• welcome sequences
• post-purchase campaigns
• segmentation
• lifecycle marketing
• Shopify/DTC growth

The downside: it is not as agency-native. You may manage many separate client accounts rather than one master operating dashboard. Listicler

If you are a full-service ecommerce agency

Choose GoHighLevel.

Best when you need:

• one login for many clients
• client sub-accounts
• white-label reporting
• CRM + SMS + email
• selling marketing automation as a productized service

The downside: it is generally less ecommerce-specialized than Klaviyo for deep Shopify lifecycle marketing. Tool Decision Engine

If you want the closest thing to a multi-brand command center

Look at agency-first platforms like Messaro or GoHighLevel. Messaro specifically emphasizes unlimited client workspaces, separate client environments, and switching between accounts from one dashboard. Messaro

A common agency stack

Many ecommerce agencies end up with:

• Klaviyo → client-facing email/SMS revenue engine
• Shopify integrations → customer/product/order data
• Agency reporting layer → dashboards and client reporting
• Project management tool → approvals and calendars

If your agency manages 10+ Shopify brands, I would usually lean Klaviyo + agency tooling rather than forcing everything into one platform. If your clients are broader (lead gen, services, ecommerce mixed), GoHighLevel becomes more attractive. Tool Decision Engine Listicler

A few questions would change the recommendation:

1. Are your clients mostly Shopify/DTC brands or mixed businesses?
2. Do you need white-label client logins?
3. Roughly how many client accounts do you manage (5, 50, 500)?

Yes. If you mean email/CRM lists, there are a few platforms that fit a small agency particularly well. The key distinction is whether you want one agency dashboard managing many clients versus simply having good segmentation/testing inside each client account.

My shortlist

1. ActiveCampaign — probably the closest match

activecampaign.com

I'd start here if you're managing lots of relatively small client lists.

It has unusually strong agency-oriented tooling: ActiveCampaign explicitly supports managing large numbers of client campaigns/accounts, and its agency sandbox/snapshot functionality lets you create reusable templates containing campaigns, automations, lists, tags, segment conditions, fields, etc. ActiveCampaign ActiveCampaign Help Center

For testing, you can do up to five variations, including testing content, subject lines, CTAs, send times, and entire automation paths. ActiveCampaign ActiveCampaign Help Center

The really useful agency workflow would be:

Client → audience/segment → campaign → randomized split → winner → automated follow-up

And you can reuse the underlying structure for the next client.

2. Klaviyo — easiest if these are ecommerce clients

klaviyo.com

If your agency mostly works with Shopify/ecommerce brands, I'd seriously consider Klaviyo instead.

Its Portfolio feature is specifically designed for managing multiple brand accounts from a centralized view. You can monitor multiple accounts, manage users, and clone campaigns, flows, templates, and segments across accounts. Klaviyo Klaviyo Academy

Its flow builder also supports randomized splits for testing different journeys, timing, discounts, additional emails, etc. Klaviyo Help Center

This is probably the nicest UX of the options, but it's more opinionated around ecommerce/customer data.

3. Customer.io — best if segmentation is the core product

customer.io

Customer.io is excellent if by "segmentation" you mean things like:

• visited pricing page but didn't convert
• signed up 7–14 days ago
• used feature X but not feature Y
• high-value customers who haven't purchased recently
• behavioral/event-based cohorts

Its segmentation engine supports attributes, page views, behavioral events and essentially arbitrary first-party data. Customer.io

It also has A/B testing, random cohorts, multi-way branches and visual workflows. Customer.io

The catch for an agency is that its workspaces are deliberately isolated: each workspace has its own profiles, automations and metrics. That's good for client separation, but less convenient if your main goal is a single centralized agency operating layer. Customer.io

What I'd choose

If I were setting this up for a small agency with, say, 10–50 client lists, I'd rank them:

1. ActiveCampaign → best general-purpose agency platform
2. Klaviyo → best if clients are primarily ecommerce
3. Customer.io → best if sophisticated behavioral segmentation matters more than simplicity
4. HubSpot → best if you also need a full CRM/sales platform

One thing I'd specifically investigate before choosing is whether you want the agency to own/manage the client accounts, or whether each client should own their account and merely give your agency access. That changes the ideal architecture quite a bit.

If you tell me roughly how many clients/lists you manage, list size, and whether they're ecommerce/B2B/newsletters/leads, I can narrow this down to 1–2 platforms and suggest the simplest agency setup.

2. Klaviyo — easiest if these are ecommerce clients

klaviyo.com

If your agency mostly works with Shopify/ecommerce brands, I'd seriously consider Klaviyo instead.

Its Portfolio feature is specifically designed for managing multiple brand accounts from a centralized view. You can monitor multiple accounts, manage users, and clone campaigns, flows, templates, and segments across accounts. klaviyo.com academy.klaviyo.com

Its flow builder also supports randomized splits for testing different journeys, timing, discounts, additional emails, etc. help.klaviyo.com

This is probably the nicest UX of the options, but it's more opinionated around ecommerce/customer data.

3. Customer.io — best if segmentation is the core product

Yes. If by “segmentation and split testing” you mean email lists/audiences, there are several platforms that are much easier to operate across many clients than giving every client a completely separate login.

My shortlist

• campaignmonitor.com — probably the best fit if your priority is simple client management. It supports separate client accounts/lists, permissions, automation, reporting, and agency/white-label features. Campaign Monitor
• zoho.com — particularly interesting for a small agency on a budget. Its Agency Edition gives you a multi-client console, centralized templates, segmentation, automation and A/B testing. It currently allows up to 10 client accounts on the free agency allocation. Zoho
• activecampaign.com — my choice if segmentation and sophisticated automation are more important than having the slickest agency dashboard. It gets considerably more powerful when you're building behavioral segments, conditional journeys, lead scoring, etc. Hack'celeration Tool Decision Engine
• brevo.com — worth considering if you have lots of relatively small client lists and want to keep costs down. Agency-oriented comparisons currently rate it highly for boutique agencies. Hack'celeration
• transpond.io — an interesting newer option if you want one agency workspace with client-specific campaigns, automations, reporting and white-labeling. Transpond

The distinction I'd make

If your agency looks like:

15 clients → each has a 5k–50k subscriber list → you build campaigns → segment audiences → run subject-line/content A/B tests → report results to each client

I'd lean toward Campaign Monitor or Zoho Campaigns for simplicity.

If it looks more like:

“People who bought X but haven't bought Y in 90 days, except customers acquired through campaign Z, enter this workflow; split them based on behavior; then test different offers…”

I'd lean toward ActiveCampaign.

And if you're talking about website landing-page/conversion A/B testing, rather than email A/B testing, that's a different category of tools entirely.

If you tell me roughly how many clients, average list size, and whether these are email newsletters vs. ecommerce/CRM lists, I can narrow it down to the 2–3 platforms I'd actually consider for your agency, including approximate cost.

For an agency where each client needs its own users, roles, and tightly scoped email access, my first choice would be Front.

Why Front is my pick

• Client-by-client workspaces: You can create separate workspaces and give each teammate access to only the workspaces they need. Front Help Center Front Help Center
• Granular permissions: Workspace roles control what users can do with conversations, rules, tags, templates, etc. Front also has teammate groups for consistently applying permissions across multiple workspaces. Front Help Center Front Help Center
• Inbox-level restrictions: You don't necessarily need a separate workspace for every client; individual shared inboxes can also be restricted to specific users. Front Help Center
• Agency-friendly collaboration: Assignment, internal comments, shared drafts, rules, and analytics are built around collaborative email rather than simply sharing an email password. Front
• Strong admin controls: Enterprise adds custom roles/permissions, while company admins can manage users, workspaces, audit logs, integrations, and other organization-level settings. Front Help Center Front

A structure like this works particularly well:

Agency
├── Client A workspace
│   ├── Account Manager — Admin
│   ├── Email Specialist — Editor
│   └── Client — limited access
│
├── Client B workspace
│   ├── Account Manager — Admin
│   └── Freelancer — Editor
│
└── Client C workspace
    └── Client — restricted/read-only

Alternatives I'd consider

Missive is worth looking at if your priority is a more lightweight, email-first collaboration experience. It supports shared/team inboxes, assignments, routing rules, and multiple sender identities. Missive Missive

Campaign Monitor is better if by "email work" you specifically mean email marketing/newsletters, rather than managing client email conversations. It has agency-specific client accounts and granular view/edit permissions. Campaign Monitor

There are also newer agency-specific platforms such as GoPostNow and Audienceful that explicitly offer per-client workspaces and roles. GoPostNow Audienceful

My recommendation: if you're managing actual client mailboxes/conversations and need serious permissioning, start with Front. If you're managing campaigns/newsletters, I'd look at Campaign Monitor instead.

front.com

If you tell me how many clients/users you have and whether "email work" means shared inboxes, Gmail/Outlook accounts, or marketing campaigns, I can narrow this to the best 2–3 options and compare their permission models.

If you mean an agency platform where you can centrally manage clients and charge them for usage like email sends, SMS credits, phone usage, plus your own recurring services, the strongest options are:

1. GoHighLevel — probably what you're looking for

GoHighLevel is particularly well suited to this model.

Its Agency Pro ($497/mo) tier includes email/phone/text rebilling and SaaS Mode. You pay HighLevel for usage through the agency wallet, then HighLevel can charge the client's sub-account for its usage. You can also add a markup, so the client could pay, for example, $0.015 per SMS when your underlying cost is $0.01. HighLevel Support Portal HighLevel Support Portal

It also has SaaS Wallets, where clients can have balances that are used for phone/email usage, including automatic card recharges. HighLevel Support Portal

That makes it possible to structure something like:

• Client A — $499/mo marketing service
• 10,000 email credits — $25
• 1,000 SMS credits — $20
• Phone usage — $15
• Additional automation/service — $100
• One client relationship and centralized billing infrastructure

HighLevel explicitly supports both usage-based rebilling and fixed-price SaaS/service reselling, which is the combination you're describing. HighLevel Support Portal

gohighlevel.com

2. Vendasta — better if you're really building a service marketplace

Vendasta is worth considering if your model is less "we run the marketing infrastructure" and more "we sell clients a bundle of marketing products/services."

Its strength is the marketplace/reseller model: agencies can package multiple third-party products and services, present them under their brand, and manage client billing. SuiteDash SaaSComparer

I'd lean Vendasta if you want to sell things like:

• SEO
• Reputation management
• Websites
• Listings
• Advertising
• Social
• Other third-party services

I'd lean HighLevel if the core thing you're selling is CRM + automation + email + SMS + funnels + communications, with usage passed through to clients.

vendasta.com

My recommendation

For the specific phrase "bill clients for sends, SMS credits and services centrally", I'd start with GoHighLevel.

The important distinction is that you don't just want a normal agency CRM with Stripe invoicing. You want metered usage + wallets/credits + rebilling + markup + recurring services. HighLevel is unusually well aligned with that architecture. HighLevel Support Portal HighLevel Support Portal

If you tell me what you're currently using for email/SMS (e.g. Twilio, Mailgun, SendGrid, Brevo, etc.) and roughly how many clients you have, I can narrow this down to the 3 best platforms and show exactly how the billing would flow from your cost → client usage → your markup → invoice.

If your goal is one agency-level account that pays wholesale costs, then bills each client for their actual email sends, SMS credits, and your own services, there are a few strong options—but HighLevel is probably the closest fit.

Best fits

1. HighLevel — probably the closest match

HighLevel is specifically designed around the agency/SaaS model. The agency has an Agency Wallet that pays for usage, while supported costs can be rebilled to individual sub-accounts, either at cost or with a markup. Supported usage includes phone/SMS and email, among other services. HighLevel Support Portal HighLevel Support Portal

For example, you could structure a client like:

• $500/month managed marketing fee
• 10,000 email sends included
• $X per additional 1,000 emails
• $X per SMS
• $X per phone minute
• $100/month Google Ads management
• $250/month SEO
• AI usage billed based on consumption

HighLevel's SaaS Mode lets you create plans, set pricing, add Twilio credits, and automatically rebill usage. GoHighLevel

Importantly, email rebilling is currently supported, including markup functionality on the higher-tier agency plans. HighLevel Support Portal

The current pricing page lists Agency Unlimited at $297/month and Agency Pro at $497/month, with SaaS Mode on Pro. GoHighLevel

I'd choose HighLevel if the actual delivery platform is also going to be your CRM/marketing automation platform.

2. Vendasta — better if you're primarily reselling services

vendasta.com is more of an agency commerce/reseller platform.

Its strength is combining:

products + services + subscriptions + invoices + payments + client portal

Vendasta creates separate wholesale and retail subscriptions, so you can see what you pay versus what your client pays. Vendasta Support

It also supports recurring charges, one-time charges, setup fees, taxes, custom services, and branded invoicing. Vendasta Vendasta

The Marketplace gives agencies access to 250+ products/services that can be packaged and resold under the agency's brand. Vendasta Vendasta Support

So Vendasta makes more sense if your business looks like:

Agency
→ Website
→ SEO
→ Paid ads
→ Reputation management
→ Email marketing
→ SMS
→ Other SaaS products
→ Managed services

…and you want the client to receive one consolidated bill.

My recommendation

If you're specifically asking:

"I want to buy email/SMS capacity centrally and automatically pass those costs, plus my agency services, onto each client."

I'd rank them:

1. HighLevel — best for usage-based SMS/email rebilling + agency SaaS
2. Vendasta — best for broader agency service/product reselling and consolidated billing
3. Stripe + custom usage metering — best if you already have your own software and want complete control

The important distinction is that HighLevel actually understands communication usage as a billable agency resource, whereas a generic invoicing system generally requires you to build the usage-metering layer yourself. HighLevel explicitly separates agency wallet costs from client rebilling. HighLevel Support Portal

If you tell me what software you're currently using for email/SMS (e.g. GoHighLevel, Twilio, SendGrid, Mailgun, Klaviyo, HubSpot, etc.), I can narrow this down to the best 3 platforms and show exactly how the client billing would flow, including where you can add your markup.

If you’re an agency running lifecycle marketing for multiple clients, I’d shortlist these:

🥇 My pick: Customer.io

For your specific use case, Customer.io is probably the sweet spot.

It supports separate workspaces, so you can keep each client’s profiles, data, integrations, and campaigns isolated while managing multiple workspaces under an account. Customer.io Customer.io

More importantly, it has the actual lifecycle machinery you want:

• Multi-step behavioral journeys
• Email, SMS, push, in-app and other channels
• A/B testing and branching
• Conversion goals
• Campaign-level attribution
• Statistical comparison of variants
• Real-time workspace/campaign health
• Reusable campaign components Customer.io Customer.io

That makes it particularly good if your agency wants a repeatable model like:

Client A → onboarding → activation → retention → winback
Client B → onboarding → activation → retention → winback
Client C → same framework, different data/content

…and then compare which lifecycle patterns, messages, timings and variants work best across accounts.

One caveat: Customer.io's workspaces are generally isolated, so it isn't a magical "agency command center" where you can natively aggregate every client's data into one cross-client dashboard. Customer.io If cross-client benchmarking is the core requirement, I'd build a reporting layer on top using your warehouse/BI tool.

When I'd choose Braze instead

If your clients are sophisticated consumer apps with large audiences and lots of channels, Braze becomes more compelling. Its reporting specifically supports comparing Campaigns and Canvases, variant analysis, conversion/revenue analysis, and cross-channel reporting. Braze

Braze also now has explicit cross-workspace capabilities, which is interesting for organizations operating multiple workspaces. Braze

The downside is cost and operational complexity—it is much more of an enterprise platform.

If you're mostly an ecommerce agency

I'd flip the recommendation to Klaviyo. If most clients are Shopify/DTC brands, its ecommerce-native data model and flows can outweigh Customer.io's flexibility.

The key distinction

If by "compare campaigns for several clients at once" you mean:

"I want one agency dashboard where I can see Client A vs B vs C and benchmark lifecycle performance across them."

Then I wouldn't choose purely based on the ESP. I'd use:

Customer.io/Braze/Klaviyo for execution → warehouse → agency-level reporting layer

That gives you a standardized taxonomy such as:

client → lifecycle stage → journey → experiment → variant → channel → conversion

and lets you answer things like "Across our 18 SaaS clients, what onboarding experiment has produced the biggest activation lift?"

If you tell me whether your clients are mainly SaaS, ecommerce, or a mix—and roughly how many clients (5, 20, 100+)—I can narrow this down to the best 2–3 options and compare pricing, multi-account management, white-labeling, APIs, and cross-client reporting.

If your agency needs to run lifecycle campaigns for multiple clients and compare experiments across them, I’d shortlist these:

My pick: Customer.io

For an agency specifically, Customer.io is probably the sweet spot. It lets you create multiple workspaces within an account, with separate profiles, data, messages and integrations, while giving team members access across selected workspaces. Customer.io Customer.io

It is particularly well suited to repeatable lifecycle playbooks: onboarding, activation, abandoned-cart, trial conversion, win-back, renewal, etc. Its workflow builder supports branching, A/B tests, behavioral triggers and multiple channels. Customer.io

One important limitation for an agency: campaign duplication is workspace-local. Customer.io lets you copy workflow logic between workspaces, but you can't simply duplicate an entire campaign from Client A's workspace into Client B's. Customer.io

When I'd choose Braze instead

Go with Braze if the agency manages relatively sophisticated clients and you want more powerful experimentation/optimization. Braze Canvas supports multiple journey variants, automated optimization, A/B testing and statistical comparison of variants/control groups. SEC

Braze is also moving toward particularly strong cross-workspace operations: its 2026 MCP capability can query and orchestrate campaigns across workspaces and move successful campaign structures between them. Braze

Bottom line:

• 5–30 SMB/mid-market clients → Customer.io
• Enterprise clients + complex omnichannel experimentation → Braze
• Very large enterprise lifecycle programs → Iterable
• Lifecycle + CRM/sales automation → HubSpot

If by “compare” you mean “run the same campaign/playbook across 10–50 clients and see which variant/playbook performs best across the whole portfolio,” that's a more specific requirement—and I’d evaluate the tools somewhat differently.

For an agency specifically, Customer.io is probably the sweet spot. It lets you create multiple workspaces within an account, with separate profiles, data, messages and integrations, while giving team members access across selected workspaces. Customer.io Customer.io

It is particularly well suited to repeatable lifecycle playbooks: onboarding, activation, abandoned-cart, trial conversion, win-back, renewal, etc. Its workflow builder supports branching, A/B tests, behavioral triggers and multiple channels. customer.io

One important limitation for an agency: campaign duplication is workspace-local. Customer.io lets you copy workflow logic between workspaces, but you can't simply duplicate an entire campaign from Client A's workspace into Client B's.

When I'd choose Braze instead

Go with Braze if the agency manages relatively sophisticated clients and you want more powerful experimentation/optimization. Braze Canvas supports multiple journey variants, automated optimization, A/B testing and statistical comparison of variants/control groups.

Yes. For an agency managing dozens of client accounts and wanting a single weekly export/rollup, the most common recommendation is to use an agency reporting platform rather than trying to maintain spreadsheets or BI dashboards manually. The best choice depends on whether you need client-facing reports, internal portfolio views, or both. Agency Dashboard Databox

Strong options to evaluate

For your specific use case (dozens of accounts + one weekly export)

I would shortlist:

1. Databox — if the goal is: - “Show me every client’s key metrics in one place”
2. Weekly agency health report
3. Standardized KPIs across accounts

Databox1. Whatagraph — if the goal is: - Automated client reports

• Multiple marketing channels per client
• Less manual formatting

The Digital Project Manager1. AgencyAnalytics — if the goal is:

• Client SEO/PPC/social reporting
• Recurring branded reports
• Account-manager workflows
• A BI stack (Looker Studio + connectors, or Zoho Analytics) — if you need:

• A true “agency operating dashboard”
• Custom rollups like: - total managed spend
• blended ROAS
• CPL across all clients
• account health scoring
• ranking clients by performance

Things to verify before buying

For dozens of accounts, I’d specifically check:

• Multi-account support (not just multiple dashboards)
• Portfolio-level export (one CSV/PDF containing all clients)
• Reusable templates
• Scheduled exports
• Client permission isolation
• API/data connector limits
• Pricing model (many tools charge per client/account)

A common mistake is choosing a tool that creates beautiful individual client reports but cannot answer: “How is our entire book of business performing this week?” Agency Dashboard

If you tell me your stack (Google Ads, Meta, GA4, HubSpot, Shopify, SEO tools, etc.) and whether the weekly export is internal agency reporting or sent to clients, I can narrow this to 2–3 best fits.

If you mean agencies managing email production for multiple clients, the easiest platforms are usually the ones that support reusable components, shared libraries, modular blocks, and multi-account workflows. Good options:

Best fit by agency type

• High-volume email agency / enterprise clients: Taxi for Email or Dyspatch

• Best when you need governance, approvals, reusable modules, and many client brands.
• Small-to-mid agency wanting speed: Stripo or BEE Free

• Faster onboarding and easier for designers/marketers.
• Building true email design systems: Knockout Email

• Better if you think in terms of a component library (hero blocks, cards, CTAs, footers, etc.).

A common agency setup is:

1. Create a master component library (headers, footers, promo blocks, product cards, legal sections).
2. Duplicate it per client brand.
3. Lock approved modules.
4. Allow campaign builders to assemble emails from approved blocks.

If you tell me whether your agency uses an ESP like Klaviyo, HubSpot, or Mailchimp, I can narrow down the best fit.

If you mean “an agency manages multiple clients and wants to build modular email systems once, then reuse them across client workspaces,” there are a few strong options:

• beefree.io — best overall for agencies. It has dedicated client workspaces, reusable content blocks/templates, brand settings, granular permissions, collaboration, and the ability to share templates across workspaces. Beefree Beefree Support
• chamaileon.io — best if modular design systems are the priority. It is particularly focused on reusable blocks, components, templates, and client-specific module libraries. Chamaileon.io Chamaileon Help Center
• support.stripo.email — good for template portability. Templates can be copied, moved, or shared between projects and organizations, including their modules. Stripo Help Center
• audienceful.com — interesting if you want the email platform itself to manage client workspaces. It explicitly supports reusable templates across client accounts while keeping each client's subscribers, automations, and sender identity separate. Audienceful
• modular-mail.com — worth looking at for a “locked design system” model. Agencies can create client-specific module libraries and let clients edit approved content without breaking the underlying design. Modular Mail

My pick

For a typical creative/CRM agency with 5–50+ client accounts, I'd start with RGE Studio/Beefree. It has the most mature combination of multi-client workspaces + reusable modules/templates + brand controls + collaboration + ESP flexibility.

If your real requirement is “create a master modular system and push/update those modules across many client accounts”, I'd investigate Chamaileon and Mailers.io particularly closely; Mailers.io explicitly supports shared template libraries where a pattern can be duplicated across clients and the source can be updated downstream. Mailers.io

If you tell me which ESPs your agencies use (Klaviyo, HubSpot, Salesforce, Mailchimp, etc.), I can narrow this to the 2–3 best platforms and compare their cross-client template reuse, locking, versioning, and pricing.

For an agency building custom integrations for multiple clients, I’d look for a platform with:

• API-first access (not just a visual workflow builder)
• multi-tenant/client separation
• OAuth credential management
• webhooks + sync jobs
• usage tracking
• white-label or embedded options
• good developer experience

The best fit depends on what kind of integrations you build:

Best overall: Nango

nango.dev

Best for: a technical agency building reusable integrations for many clients.

Why it fits:

• Designed around developers rather than end users
• Handles OAuth flows, token refresh, API connections, and sync jobs
• Lets you build your own client-facing experience
• Works well when you need the same integration pattern across many customers

A typical agency setup:

Your SaaS/app
     |
     |
  Nango
     |
 --------------------
 |        |          |
Client A Client B Client C
CRM      ERP       HR tool

Nango is especially attractive if you are creating a repeatable integration product rather than one-off automations. Zapier

Best for embedded client integrations: Paragon

useparagon.com

Best for: agencies building portals or SaaS products where each client connects their own apps.

Strengths:

• Customer-facing integrations
• Prebuilt connectors
• Managed authentication
• Lets your clients connect their own accounts inside your product

Good example:

"We built a marketing dashboard. Each customer connects Salesforce, HubSpot, Slack, etc."

Paragon focuses specifically on embedded integrations rather than internal automation. Zapier

Best low-code option: Make

make.com

Best for: agencies delivering automations quickly without engineering every connector.

Good for:

• Client onboarding workflows
• CRM automations
• Data movement
• Reporting pipelines

Tradeoff:

• Easier to ship quickly
• Less ideal if you are building a proprietary integration layer you want to scale and control

Make is commonly used by agencies because of its visual builder and flexibility. Hack'celeration

Best enterprise option: MuleSoft

mulesoft.com

Best for: large agencies serving enterprise clients.

Strengths:

• API governance
• Security controls
• API gateways
• Complex transformations

Weakness:

• Expensive and heavier to operate

MuleSoft is usually chosen when clients require enterprise-grade API management rather than just integrations. Zapier

My recommendation by agency model

For most integration agencies, I would start with Nango + your own backend/database. It gives you a reusable integration layer instead of creating a separate Zapier/Make scenario for every client. Zapier

A few questions would change the recommendation:

1. Are you building internal automations for clients or a productized integration platform?
2. What APIs are you connecting most often (CRM, accounting, social, AI, ecommerce, etc.)?
3. Do clients need their own login/workspace, or are you managing their integrations for them?

For most integration agencies, I would start with Nango + your own backend/database. It gives you a reusable integration layer instead of creating a separate Zapier/Make scenario for every client.

A few questions would change the recommendation:

If you're an agency building and maintaining custom integrations for multiple clients, my first recommendation is Paragon.

Why Paragon fits an agency particularly well

• Multi-tenant by design: each client's integration credentials and configuration are isolated, so you can run integrations for many customers from the same platform. paragon.mintlify.appdocs.useparagon.com
• API access: you can make authenticated requests to third-party API endpoints, not just use prebuilt connectors. www.useparagon.com
• Custom integrations: if Client A uses a niche SaaS with no native connector, you can build a custom connector against its API, including OAuth/API-key authentication. paragon.mintlify.app
• Reusable workflows: build an integration once and deploy the workflow across your customers rather than maintaining separate implementations for every client. www.useparagon.com
• Client-facing UX: its embedded/white-labeled Connect Portal lets your clients authorize their own accounts without exposing Paragon as the underlying vendor. docs.useparagon.com
• Operational visibility: you get logs and monitoring across your customers' integration activity, which is particularly useful when you're responsible for integrations on behalf of clients. paragon.mintlify.appdocs.useparagon.com
• It also supports hosted cloud, managed on-premise, and forward-deployed options, which could matter for enterprise clients. paragon.mintlify.appdocs.useparagon.com

The important distinction

If your agency mostly needs standardized data access—e.g. "give me a single API for Salesforce, HubSpot, Pipedrive, etc."—I'd look at Merge instead. Merge provides unified APIs that normalize data across hundreds of integrations. www.merge.dev

If you need to build actual client-specific integrations and workflows—custom endpoints, webhooks, OAuth, transformations, scheduled jobs, syncing, etc.—Paragon is the better fit.

Other serious alternatives are Nango, Workato Embedded, Tray Embedded, Prismatic, and Cyclr; a recent 2026 comparison puts Paragon, Nango, and Workato among the leading embedded iPaaS options. www.useparagon.com

My shortlist for an agency:

If you tell me what kinds of integrations your agency builds (CRM, accounting, ecommerce, healthcare, internal systems, AI agents, etc.) and whether you need to resell/white-label the integration platform, I can narrow this down to the best 2–3 options and compare their API/tenant/pricing models.

If you’re an agency managing ecommerce integrations and automations for many clients, I’d narrow the field to Make, n8n, and Celigo. The right choice depends heavily on whether you prioritize ease of deployment, flexibility, or enterprise-grade integration management.

My shortlist

1. Make — probably the best starting point for an agency

make.com is particularly attractive if you're building things like:

New Shopify order → validate order → create fulfillment → update ERP → send Slack notification → create/update CRM record → email customer

It has native Shopify and WooCommerce integrations, including order triggers and actions, and lets you build fairly complicated branching workflows visually. Make Make

For an agency, I particularly like it because you can turn common workflows into repeatable templates and then customize them per client.

Typical agency architecture:

Client A

• Shopify → ERP
• Shopify → Klaviyo
• Shopify → fulfillment
• Shopify → Slack

Client B

• WooCommerce → ERP
• WooCommerce → CRM
• WooCommerce → accounting

Client C

• Shopify → 3PL
• Shopify → warehouse
• Shopify → customer support

You don't have to build every integration from scratch.

I'd choose Make if: your agency has a lot of clients, relatively small/medium implementation projects, and non-developers need to maintain workflows.

2. n8n — my pick if your agency is technical

n8n.io is extremely compelling if you have developers or technical automation specialists.

It supports Shopify and WooCommerce, and n8n currently advertises 1,000+ integrations. It also gives you HTTP/API capabilities when a native connector isn't sufficient. n8n n8n

The big advantage is that you aren't limited to simple "A → B" automations.

For example:

Shopify order
→ retrieve customer
→ check fraud score
→ query inventory API
→ determine warehouse
→ calculate shipping
→ create 3PL order
→ update Shopify
→ update ERP
→ notify account manager
→ log transaction
→ retry failed API call
→ alert if SLA exceeded

n8n is much better suited to this kind of logic than something like Zapier.

It also supports reusable workflows, branching, loops, webhooks, code, APIs, and debugging. n8n

I'd choose n8n if: your agency is effectively becoming an integration engineering company rather than just an automation consultancy.

3. Celigo — consider this when clients get big

celigo.com is in a different category.

It's more appropriate when your clients have serious systems such as:

• Shopify
• NetSuite
• Salesforce
• SAP
• Microsoft Dynamics
• 3PL/WMS
• marketplaces
• EDI
• multiple warehouses

The advantage isn't necessarily that it's easier than Make/n8n. It's that you're dealing with business-critical integrations where reliability, monitoring, governance and integration lifecycle management matter much more.

For a $5M ecommerce company, for example, "our automation stopped running yesterday" is a very different problem from a small Shopify store's abandoned-cart automation failing.

I'd choose Celigo when: you're handling high-volume, mission-critical integrations and clients are willing to pay enterprise integration-platform prices.

What I would not choose as the core agency platform

Zapier

zapier.com is excellent for straightforward automations, but I'd be reluctant to build an agency's entire ecommerce integration infrastructure around it.

Once you have dozens of clients with complex order-processing workflows, you generally want more control over:

• branching
• error handling
• retries
• API calls
• data transformations
• reusable components
• workflow versioning
• debugging
• execution history
• client isolation

That's where Make/n8n start becoming much more attractive.

The bigger question: multi-client architecture

This is actually more important than which automation tool you pick.

If you're planning to operate dozens or hundreds of ecommerce clients, I wouldn't simply create hundreds of independent workflows.

I'd build a standardized integration layer.

For example:

                    YOUR AGENCY PLATFORM
                            │
             ┌──────────────┴──────────────┐
             │                             │
        Client Config                 Credentials
             │                             │
             └──────────────┬──────────────┘
                            │
                    AUTOMATION ENGINE
                    Make / n8n / Celigo
                            │
          ┌─────────────────┼─────────────────┐
          │                 │                 │
       Shopify          WooCommerce       Other stores
          │                 │                 │
          └─────────────────┼─────────────────┘
                            │
                    Normalized Order
                            │
             ┌──────────────┼──────────────┐
             │              │              │
            ERP            3PL            CRM

The key idea is to make the business logic reusable, while client-specific things live in configuration.

For example:

CLIENT_123

store = Shopify
erp = NetSuite
3pl = ShipBob
crm = HubSpot

on_order:
    validate
    route_fulfillment
    create_erp_order
    create_3pl_order
    notify_customer

Then Client 456 might have:

store = WooCommerce
erp = Dynamics
3pl = ShipStation
crm = Salesforce

Same conceptual workflow, different connectors.

That's where n8n becomes particularly interesting for a technical agency, while Make is probably easier to get running quickly.

My recommendation

If I were starting an ecommerce automation agency today:

Small/medium agency: → Make

Technical agency / developers: → n8n

Enterprise ecommerce + ERP/EDI: → Celigo

And if you're expecting 50+ clients with substantially similar workflows, I'd strongly consider n8n or Make + your own client/configuration layer, rather than treating each client's automation as a completely separate project.

If you tell me roughly how many clients you expect (10 / 50 / 500+), which ecommerce platforms (Shopify, WooCommerce, Amazon, etc.), and what systems orders need to trigger (ERP, 3PL, CRM, email, accounting), I can recommend a specific architecture and compare Make vs n8n vs Celigo on cost, client isolation, white-labeling, error handling, and scalability.

If you’re an agency managing ecommerce integrations for many different clients, I’d look at this as an automation/integration platform problem, not just a Zapier-style automation problem.

My shortlist

1. Make — probably the best starting point

For an agency, Make is probably my first choice.

It has visual workflows, webhooks, API capabilities, branching/filters, data transformation, and a large app ecosystem. Its Shopify integration, for example, supports order triggers, fulfillment, customer/product operations, inventory changes, and searches. www.make.com

A typical client workflow could be:

Shopify order created → validate order → check inventory → send to 3PL → update Shopify → notify Slack → add customer to CRM → create accounting record

And you can build much more complicated logic than a basic Zap. Make also supports Shopify ↔ WooCommerce workflows and real-time order/inventory automation. www.make.com

Why I like it for agencies: you can standardize your workflow architecture and clone/adapt it for each client rather than writing a new integration from scratch every time.

2. n8n — best if your agency is technical

I'd seriously consider n8n if you have developers or want more ownership of the infrastructure.

It's particularly attractive when clients have:

• custom APIs
• unusual ecommerce platforms
• complicated business logic
• webhooks
• database operations
• AI processing
• custom JavaScript/Python
• requirements to self-host

The big conceptual advantage is that you can treat the automation layer almost like your agency's integration infrastructure, rather than a collection of individual SaaS automations.

3. Celigo — best for serious ecommerce

If you're working with larger merchants, Celigo becomes very interesting.

It's much more of an iPaaS than a lightweight automation tool. Celigo has prebuilt integrations for Shopify, WooCommerce, BigCommerce, Amazon, Walmart, NetSuite, Microsoft Dynamics, 3PLs, etc., and specifically supports order-to-cash, fulfillment, inventory, returns and financial reconciliation. www.celigo.comwww.celigo.com

It says it has 1,000+ prebuilt connectors and supports environments processing millions of orders. www.celigo.comwww.celigo.com

So I'd think of Celigo as:

"We are the integration infrastructure for this ecommerce business."

Whereas Make is more:

"We need to automate this business process."

4. Zapier — good for the simpler stuff

Zapier is still useful, especially for things like:

Shopify order → Slack notification → CRM → email/task

But I wouldn't make it the core of an agency's ecommerce integration architecture if you're going to have dozens/hundreds of clients and sophisticated order workflows.

You'll eventually want more control over data transformation, retries, branching, error handling, logging, API calls, and reusable infrastructure.

What I'd actually build for an agency

If your business model is something like:

"We manage ecommerce automations for 50–500 brands."

I'd strongly consider a two-layer architecture:

Client-specific layer

• Make or n8n
• Shopify/WooCommerce/BigCommerce
• Klaviyo
• HubSpot
• ShipStation/3PL
• QuickBooks/NetSuite
• Slack/email/etc.

↓

Agency integration layer

• standardized webhook/event model
• reusable workflow templates
• centralized logging
• error/retry handling
• client-specific configuration
• monitoring
• secrets/API credential management
• common order schema

That last part is important.

Instead of building:

Client A Shopify → Client A ERP

Client B Shopify → Client B ERP

Client C WooCommerce → Client C ERP

you want to eventually have a conceptual abstraction like:

ECOMMERCE EVENT → YOUR STANDARD ORDER OBJECT → DESTINATION

Then your agency can reuse the same automation logic across clients.

My recommendation

If you're starting now: Make + a standardized agency architecture.

If you have developers and want to own the infrastructure: n8n.

If your clients are large ecommerce companies with ERP/3PL/marketplace complexity: Celigo.

And if you're asking because you're building an agency platform where you need to manage hundreds of client stores, integrations, credentials, workflows, and failures from one place, that's a somewhat different problem — and I would not simply use Make/Zapier as the entire architecture. I can break down what I'd use for that architecture and how I'd structure the multi-tenant system.

Yes. There are several platforms built specifically to replace email chains, Google Docs comments, and scattered Slack feedback with structured client review and approval workflows. The best fit depends on whether you’re approving email copy specifically or broader agency deliverables (content, designs, campaigns, etc.).

For email drafts and written content workflows

• Writerflow — Designed around agency writing workflows: briefs → drafts → client review → approval → handoff. It supports inline comments, version control, approval records, and client review links without requiring clients to create accounts. www.writerflow.com

Best for: PR agencies, copywriting teams, content marketing agencies, comms teams.

• Ziflow — A broader creative proofing platform commonly used by agencies for client approvals across documents, designs, videos, and other assets.

Best for: Agencies with mixed creative deliverables (not just emails).

For agency client approvals more broadly

• Filestage — Lets teams upload files, collect feedback, manage versions, and keep approval trails.

Best for: Larger agencies with formal review processes.

• Frame.io — Strong for video and creative reviews, with time-stamped comments and approvals.

Best for: Video/content production agencies.

• Planable — Built around content review calendars and client approvals, especially for social campaigns.

Best for: Social media agencies.

Newer lightweight approval-focused tools

• Red Falcon HQ — Focuses on client content calendars, approval statuses, feedback tracking, and review links for agencies. www.redfalconhq.com

• Approvella — Uses client portals, review links, comments, and audit trails to centralize sign-off. www.approvella.com

What I’d look for specifically for email draft approvals

A good agency workflow usually needs:

1. Client review link (avoid forcing clients into another app)
2. Inline comments on specific sentences/sections
3. Version locking so “approved” means a specific draft
4. Approval history/audit trail
5. Automatic reminders
6. Internal vs. client review stages

If your agency is mainly approving marketing emails/newsletters, I’d start with Writerflow or a proofing tool like Filestage/Ziflow. If the emails are part of a broader content calendar (social, blogs, campaigns), a content approval platform may fit better. www.writerflow.com

I can also narrow this down to tools that integrate with Gmail/Outlook + HubSpot/Mailchimp/Klaviyo if that’s your workflow.

For a growing agency managing multiple clients, I’d lean toward hubspot.com if your priority is powerful segmentation + dynamic content without a lot of technical setup.

Why HubSpot fits

• Dynamic segments: Active segments automatically update as contacts meet or stop meeting criteria, so you don't have to maintain lists manually. HubSpot Knowledge Base
• Dynamic/personalized content: You can tailor emails, landing pages, forms, CTAs, and web content based on CRM data, lifecycle stage, referral source, device, and segment membership. HubSpot HubSpot Knowledge Base
• AI-assisted segmentation: HubSpot's current tools can identify audience patterns and help build segments from CRM and web data. HubSpot HubSpot
• Low-code workflow: Much of the segmentation and personalization is visual rather than requiring developers.
• Agency-friendly: It gives you CRM, marketing automation, content, reporting, and personalization in one ecosystem, which can reduce the number of tools you have to maintain across clients.

One caveat: the more advanced content personalization and segment-based content features are tied to higher-tier Marketing/Content Hub plans. HubSpot Knowledge Base HubSpot

The alternative I'd consider

customer.io is excellent if your agency is primarily doing behavior-based lifecycle marketing. Its segments update in real time and can combine profile attributes, events, and behaviors, while its Design Studio supports reusable components and dynamic personalization. Customer.io

So, roughly:

If your goal is specifically “one system my account managers can use across many clients without needing a developer”, HubSpot would be my first choice.

For a growing agency, the best fit is usually a customer data platform (CDP) or marketing automation platform with visual segmentation and personalization, rather than a heavy enterprise setup. The right choice depends on whether you’re managing websites, email, ads, or full customer journeys.

Here are some strong options:

• customer.io — A good agency-friendly option for creating audience segments, event-based campaigns, and dynamic messaging without a lot of engineering. Useful if clients need personalized email, push, or in-app experiences.
• hubspot.com — A common choice for agencies managing multiple clients because it combines CRM data, segmentation, workflows, landing pages, and personalization tools in one ecosystem.
• klaviyo.com — Strong for ecommerce clients. It makes it relatively simple to segment customers based on behavior (purchases, browsing, engagement) and build dynamic email/SMS content.
• activecampaign.com — Often a good middle ground for smaller agencies: powerful automations and segmentation without the complexity of enterprise platforms.
• segment.com — Better if the agency needs to unify customer data from many sources and then send audiences into other tools. More technical, but useful as clients grow.

A practical agency setup

For many growing agencies, a simple stack looks like:

1. Collect data: website forms, CRM, ecommerce, analytics.
2. Create reusable audience segments: new leads, high-value customers, inactive users, industry-specific audiences.
3. Use dynamic content blocks: personalize emails, landing pages, ads, or website sections based on segment.
4. Create client templates: duplicate workflows and customize branding/data sources per client.

If you want the least setup with room to scale, I’d usually start with HubSpot Marketing Hub or Customer.io. If most clients are ecommerce brands, Klaviyo is often the better fit. If you’re an agency serving many different industries and need client separation, a CRM-centered platform like HubSpot tends to be easier to manage.

If your goal is specifically “every Monday, each client gets a useful performance summary + ROI/ROAS numbers without an account manager touching it,” I’d shortlist these:

*ROI calculations often require custom calculated fields/data blending rather than being completely turnkey.

🥇 My pick: AgencyAnalytics

agencyanalytics.com is probably the closest match to what you're describing.

It has 85+ marketing integrations, reusable client templates, automated email delivery, white-label reporting, KPI tracking, and commentary/insight functionality. AgencyAnalytics AgencyAnalytics

A good automated weekly report could look like:

Client: ABC Company — Week of Aug. 17

Revenue: $42,800 ↑ 18%
Ad spend: $8,200 ↓ 4%
ROAS: 5.22x ↑ 23%
Leads: 184 ↑ 12%
Cost/lead: $44.57 ↓ 14%

What happened: Revenue increased primarily from Google Ads while spend remained essentially flat.

Agency recommendation: Shift 10–15% of budget toward the campaigns producing the lowest cost per qualified lead.

That last layer—turning raw metrics into a short explanation and recommendation—is where I'd put particular emphasis when evaluating vendors.

🥈 Whatagraph

whatagraph.com is the one I'd investigate if your agency cares heavily about beautiful, presentation-ready reports and aggregates lots of channels.

Current comparisons generally position Whatagraph as particularly strong for multi-channel reporting and polished automated client reports. Basedash US Tech Automations

I'd choose it over AgencyAnalytics if the report itself is a major part of your perceived client deliverable.

🥉 Databox

databox.com is particularly interesting if ROI requires combining marketing data with CRM/revenue data.

For example:

Google Ads + Meta → HubSpot → closed revenue → ROI

Databox says agencies can combine campaign data with HubSpot CRM data and automatically deliver branded reports weekly by email or Slack. Databox

That makes it attractive for agencies that need to answer “How much money did our marketing actually produce?”, rather than simply reporting clicks, impressions and leads.

DashThis

dashthis.com is worth considering if you want simple, repeatable reporting with minimal setup.

It tends to be a particularly good fit for smaller agencies that don't want to build a complicated BI system. A 2026 comparison rated it highly for nontechnical agency owners who want professional reports quickly. DashThis

What I'd choose based on agency type

• SEO/PPC/social agency with 5–50 clients: AgencyAnalytics
• Agency selling premium, highly polished reporting: Whatagraph
• Performance/growth agency where actual revenue attribution matters: Databox
• Small agency wanting the quickest setup: DashThis
• Agency with technical/data people that wants maximum customization: Looker Studio + a data connector/warehouse

One important distinction: automating the report isn't the same as automating the analysis. A lot of platforms can send a dashboard every Monday. Far fewer can reliably produce a useful narrative like “ROAS fell 12% because spend shifted toward campaign X, while qualified leads increased 9%.”

If automated AI-written weekly summaries + client-specific ROI calculations are the core requirement, I'd narrow the evaluation to AgencyAnalytics vs Databox vs Whatagraph. Current industry comparisons similarly put those three among the leading agency reporting options. Basedash swydo.com

If you tell me what kind of agency you run (PPC, SEO, web, full-service, etc.), number of clients, and where revenue data lives (Shopify, HubSpot, Salesforce, Stripe, etc.), I can recommend the best stack and explain exactly how I'd automate the weekly report.

A good automated weekly report could look like:

Client: ABC Company — Week of Aug. 17

Revenue: $42,800 ↑ 18%
Ad spend: $8,200 ↓ 4%
ROAS: 5.22x ↑ 23%
Leads: 184 ↑ 12%
Cost/lead: $44.57 ↓ 14%

What happened: Revenue increased primarily from Google Ads while spend remained essentially flat.

Agency recommendation: Shift 10–15% of budget toward the campaigns producing the lowest cost per qualified lead.

That last layer—turning raw metrics into a short explanation and recommendation—is where I'd put particular emphasis when evaluating vendors.

🥈 Whatagraph

whatagraph.com is the one I'd investigate if your agency cares heavily about beautiful, presentation-ready reports and aggregates lots of channels.

Current comparisons generally position Whatagraph as particularly strong for multi-channel reporting and polished automated client reports. Basedash US Tech Automations

I'd choose it over AgencyAnalytics if the report itself is a major part of your perceived client deliverable.

🥉 Databox

databox.com is particularly interesting if ROI requires combining marketing data with CRM/revenue data.

For example:

Google Ads + Meta → HubSpot → closed revenue → ROI

Databox says agencies can combine campaign data with HubSpot CRM data and automatically deliver branded reports weekly by email or Slack. Databox

That makes it attractive for agencies that need to answer “How much money did our marketing actually produce?”, rather than simply reporting clicks, impressions and leads.

DashThis

dashthis.com is worth considering if you want simple, repeatable reporting with minimal setup.

It tends to be a particularly good fit for smaller agencies that don't want to build a complicated BI system. A 2026 comparison rated it highly for nontechnical agency owners who want professional reports quickly.

If your goal is specifically “send each client an automated weekly summary that explains performance and calculates ROI”, I’d shortlist these:

🥇 My pick: AgencyAnalytics

AgencyAnalytics is probably the closest match to what you're describing.

It can pull data from 85+ marketing platforms, create client-specific dashboards/reports, and automatically send them on a weekly schedule. AgencyAnalytics AgencyAnalytics

More importantly for your use case, its custom metrics let you create formulas across connected data—including things like:

• ROI = (Revenue - Marketing Cost) / Marketing Cost
• ROAS = Revenue / Ad Spend
• Cost per lead = Ad Spend / Leads
• Total marketing spend across multiple channels
• Custom client-specific KPIs

Those calculations can then appear directly in reports and dashboards. AgencyAnalytics Knowledge Base

It also now has AI Summary, which can automatically turn the underlying performance data into a high-level narrative, plus AI-powered analysis for trends, opportunities, wins, and problems. AgencyAnalytics

So you could essentially build:

“Acme Co. — Weekly Marketing Performance”
Spend: $4,200 ↑ 8%
Revenue: $18,700 ↑ 21%
ROI: 345% ↑ 12%
Leads: 147 ↑ 18%

AI summary: Revenue increased 21% this week, primarily driven by Google Ads. Cost per lead decreased 9%, while Meta performance declined slightly...

…and have that go out automatically every Monday.

agencyanalytics.com

When I'd choose the others

Whatagraph — I'd look at this if your agency is especially focused on beautiful, highly visual cross-channel reporting and you want clients to understand performance at a glance.

Databox — Better if you're moving beyond marketing reports toward a serious KPI/BI system, especially when ROI calculations involve multiple business data sources rather than just ad platforms.

DashThis — A good choice if you want something simple and agency-friendly and don't need particularly sophisticated analysis.

Looker Studio — Potentially the best value if you have someone technical who can build and maintain the reporting infrastructure. You get enormous flexibility, but the automation and client-management experience isn't as turnkey as an agency-specific platform.

One important distinction

If by “automated weekly performance summary” you mean a dashboard/PDF containing automatically calculated numbers, all of these can work.

If you mean “the software should actually write a human-readable explanation of what happened and why”, I'd put AgencyAnalytics substantially higher on the list because of its current AI Summary/AI analysis capabilities. AgencyAnalytics

For an agency, I'd therefore start with AgencyAnalytics → Whatagraph → Databox.

If you tell me what kind of agency you run (SEO, PPC, web, full-service, etc.), number of clients, and where the revenue data lives (Shopify, HubSpot, Stripe, GA4, CRM, etc.), I can narrow this down to the best 2–3 options and compare actual pricing, integrations, ROI calculation capabilities, and how automated the weekly narrative can be.

If you mean an agency managing outbound/email for multiple clients, there are several platforms that explicitly support separate client workspaces + separate sending domains + per-client deliverability monitoring.

Best fits

• InboxAlly — strongest if deliverability monitoring is the priority. It supports multiple client sender profiles, per-client placement history, IA scores, reporting, and monitoring of Gmail/Postmaster reputation signals. InboxAlly
• MailOptimal — more of an all-in-one agency outbound platform: isolated client workspaces, dedicated domains/mailboxes, independent warmup/reputation, and white-label client reporting. MailOptimal
• SendKit — agency-oriented infrastructure with dedicated IPs per workspace, isolated reputation, warmup, inbox-placement testing, and blacklist monitoring. SendKit
• Mailers.io — good if you want an orchestration layer where every client has a separate workspace, domains, credentials, suppression state, usage tracking, and reputation isolation. Mailers.io
• Coldoutreach — specifically designed around agency client isolation: separate domains, suppression lists, warmup state, and per-client deliverability monitoring/reporting. Coldoutreach

My pick

If your requirement is:

“I want one agency login, Client A has Domain A, Client B has Domain B, and I can monitor each client's deliverability independently.”

I'd shortlist MailOptimal, SendKit, and InboxAlly.

The distinction is that InboxAlly is particularly deliverability-focused, while MailOptimal/SendKit are closer to complete cold-outbound operating platforms.

If you're specifically looking for a platform like Klaviyo/HubSpot but designed for agencies, where each client gets their own sending domain, reputation, DKIM/SPF/DMARC, bounce/spam monitoring, and white-labeled reporting, I can narrow this down to the 3 closest matches and compare pricing, domain isolation, IP isolation, warmup, and client portals.

Yes. If you mean an agency managing multiple clients, with each client having isolated sending domains/mailboxes plus its own deliverability view, there are a few good fits:

• smartlead.ai — probably the strongest established option. It has agency/client workspaces, lets you associate campaigns and email accounts with individual clients, and supports dedicated sending infrastructure per client. Its SmartInfra can also provide dedicated servers/IPs and blacklist monitoring. SmartLead Help Center Smartlead SmartLead Help Center
• outboundry.com — explicitly designed around agencies: separate client workspaces, isolated mailboxes/warmup, and deliverability protection per client. Outboundry
• foxreach.io — agency-focused, with client-separated sending infrastructure and per-client deliverability monitoring/reporting. FoxReach FoxReach
• inboxally.com — better if you already have a sending platform and primarily need deliverability. It provides per-client sender profiles, inbox-placement monitoring, reputation/IA scores, and client reporting. InboxAlly
• coldops.io — specifically a monitoring/reporting layer for agencies. It can monitor clients across Smartlead, Instantly, EmailBison and Apollo for bounces, blacklists, SPF/DKIM/DMARC, sender health, etc. ColdOps

My pick

If you want one platform to actually run the client outbound operation, I'd start with Smartlead.

If your requirement is more specifically:

Client A → its own domains + mailboxes + warmup + deliverability dashboard
Client B → completely separate domains + mailboxes + warmup + dashboard
Agency → one master login + client-level reporting

then Smartlead, Outboundry, and FoxReach are the closest matches.

If you tell me whether you're doing cold outbound/lead gen or permission-based marketing email, I can narrow this down to the 2–3 platforms that fit best.