ChatGPT answers, unedited

If you mean an agency-first platform for building modular email systems and reusing them across client accounts, I’d shortlist these:

1. Modular Mail — probably the closest match. You build a template system from locked/reusable modules, define editable content fields, and give each client their own workspace. It’s specifically designed for agencies managing multiple brands. www.modular-mail.com

2. Omnisend — particularly good if your agency works with ecommerce brands. Its Partner Portal lets agencies create templated accounts, build campaigns and reusable email templates once, and copy them into client accounts. support.omnisend.com

3. Campaign Monitor — a more established all-around agency platform. It supports separate client accounts, reusable templates, locked sections, permissions, white-labeling, and centralized client management. www.campaignmonitor.com

4. Transpond — built around managing multiple clients, with reusable templates and the ability to adapt templates across accounts, plus white-labeling. transpond.io

My pick: If your main requirement is “build a modular design system once, then reuse/adapt it for many clients without clients breaking the design,” choose Modular Mail. If you need a full ESP with sending, automation, ecommerce integrations, etc., Omnisend or Campaign Monitor is likely the better fit.

If you tell me whether you're looking for Klaviyo-style sending, HTML/template production, or a white-label agency platform, I can narrow it to the best 2–3 options.

If your main requirement is “build modular email systems once, then reuse them across many client accounts,” I’d shortlist these:

My pick: Stripo

Stripo is probably the closest match. It specifically targets agencies, with reusable modules, separate client design systems, projects/folders, roles, and 90+ ESP integrations. It also supports sharing/copying templates between projects and organizations. stripo.email

If you want a more “agency operating system” feel: Beefree

Beefree for Agencies is particularly good if each client needs its own workspace and brand settings. You can create reusable content blocks/templates and manage multiple clients centrally. Its Shared Templates feature can synchronize templates across workspaces on Business/Enterprise plans. beefree.io

If you actually want templates plus sending: Zoho Campaigns

Zoho Campaigns for Agencies has an unusually direct agency workflow: create a template once and push it to specific client accounts, rather than exporting/copying manually. www.zoho.com

One interesting newer option: Modular Mail is purpose-built around locked modular templates—clients edit defined content fields without being able to wreck the underlying design. That's compelling if your agency's biggest problem is maintaining brand/design consistency after client handoff. www.modular-mail.com

Bottom line:

• Best overall for agencies: Stripo
• Best design/workspace workflow: Beefree
• Best if the platform also needs to run campaigns: Zoho Campaigns
• Best for locked, reusable design systems: Modular Mail
• Best for ecommerce agencies: Omnisend support.omnisend.com

If you mean an agency workflow where you build email modules once and reuse them across many client accounts, the best platforms depend on whether you prioritize design systems, client management, or sending.

Strong options for agencies

• knak.com — Built specifically for enterprise and agency-style email production. It focuses on reusable modules, drag-and-drop templates, brand controls, approvals, and scaling email creation across teams and clients.

• Best for: marketing agencies managing many brands with strict brand consistency.
• dyspatch.io — Lets teams create modular email components (“blocks”) that can be reused across campaigns and clients. It also supports collaboration and integrations with marketing platforms.

• Best for: agencies that want a component library approach.
• stripo.email — Popular email builder with reusable blocks, template libraries, and export options to many ESPs.

• Best for: agencies needing fast production and lots of client templates.
• beefree.io — Strong drag-and-drop builder with reusable content blocks and team collaboration features.

• Best for: smaller agencies creating polished emails quickly.
• taxiforemail.com — Designed for enterprise email production with reusable modules, governance, and handoff workflows.

• Best for: large agencies or teams producing high-volume, highly controlled email.
• parcel.io — A more developer-friendly email design system tool with reusable components and code-based workflows.

• Best for: agencies with designers/developers who want Git-like control.

Quick recommendation

• Many clients + need brand libraries: Knak or Dyspatch
• Need speed and lots of templates: Stripo or BEE
• Enterprise governance: Taxi for Email
• Design-system approach: Parcel

If you’re an agency managing dozens of client accounts, I’d look for features like:

• shared component libraries
• client-specific brand kits
• template versioning
• approval workflows
• permissions by client/team
• export to multiple ESPs (HubSpot, Marketo, Salesforce Marketing Cloud, Mailchimp, etc.)

If your main requirement is “build modular email templates once, then reuse them across many client accounts,” I’d shortlist these:

1. Zoho Campaigns — best for true cross-client template deployment. Its Agency Console lets agencies manage multiple client accounts, while its Push Template feature lets you design once and deploy approved templates directly to selected client accounts. www.zoho.com

2. Stripo — best for modular design systems. You can build reusable content modules, maintain separate brand systems for clients, and copy/share templates between projects and organizations. It also works across 90+ ESP integrations. stripo.email

3. RGE Studio (formerly Beefree) — best for agency collaboration and client workspaces. It supports separate client workspaces, reusable content blocks/templates, brand settings, permissions, and cross-workspace shared templates. beefree.io

4. Modular Mail — best if you specifically mean “modular” in the strict sense. Agencies create locked modules with editable content fields, then give each client a controlled workspace. Clients can build campaigns without altering the underlying design system. www.modular-mail.com

My pick:

• Want agency → multiple client accounts → push the same template? Zoho Campaigns.
• Want a powerful visual email builder + reusable modules across clients/ESP platforms? Stripo.
• Want locked, reusable design-system components where clients can't break the template? Modular Mail.

If you tell me whether your clients primarily use Klaviyo, HubSpot, Mailchimp, Salesforce, or different ESPs, I can narrow this down to the best 1–2 options.

If your main requirement is agencies creating modular email templates once and reusing them across multiple client accounts, a few platforms stand out:

My pick: Modular Mail

Modular Mail is probably the closest match to exactly what you're describing. You can create a library of reusable modules—hero sections, CTAs, product grids, footers, etc.—and give each client a separate workspace. The agency can control the underlying structure while clients edit only the content fields. www.modular-mail.com

It also exports clean HTML, so you're not forced to replace the client's existing ESP; it can work with platforms such as Klaviyo, HubSpot, Mailchimp, SFMC, and others. www.modular-mail.com

Modular Mail

If you want a more established visual builder: Beefree

Beefree is a strong choice if the agency wants a polished drag-and-drop design environment. Its agency offering supports separate client workspaces, client-specific brand settings, reusable content blocks, and templates. beefree.io

Beefree for Agencies

If you're primarily an ecommerce agency: Omnisend

Omnisend has a particularly useful Partner Portal: agencies can create templated accounts containing reusable campaigns, email templates, automations, forms, and segments, then copy that content into client stores. support.omnisend.com

Omnisend Partner Portal

In short: if you're building a repeatable agency template system rather than simply looking for an email-sending platform, I'd start with Modular Mail, then compare it against Beefree. If your clients are predominantly ecommerce brands, Omnisend deserves a serious look.

For agencies managing email marketing for multiple clients, the platforms that make modular, reusable email templates easiest are usually the ones with reusable blocks, brand kits, permissions, and multi-account management:

For an agency workflow specifically, I’d usually shortlist:

1. Stripo + client ESPs

Best if your team designs emails repeatedly for different brands. You can build a library of modules (hero sections, product cards, testimonials, footers, CTAs) and reuse them.

2. HubSpot

Best if clients need CRM, automation, reporting, and email in one place. It is particularly useful when each client has their own portal.

3. Klaviyo

Best for ecommerce agencies running many stores, where reusable product blocks and lifecycle flows matter.

If your priority is “build once, reuse across dozens of client accounts”, Stripo is probably the closest fit. If your priority is “manage full client marketing operations”, HubSpot is usually stronger.

If your main requirement is easy creation + reusable modular email templates across multiple client accounts, I’d shortlist these:

1. Modular Mail — probably the closest fit. It’s specifically designed around locked reusable modules, client-specific workspaces, and letting clients edit content without breaking the underlying design. Agencies can manage separate workspaces for each client. www.modular-mail.com

Modular Mail

2. Beefree / RGE Studio — stronger if you want a polished visual builder and agency workflow. It supports client workspaces, reusable content blocks, templates, brand settings, collaboration, and export to other platforms. beefree.io

RGE Studio (formerly Beefree)

3. Omnisend — particularly interesting for ecommerce agencies. Its Partner Portal lets agencies create a templated account, build campaigns/email templates once, and copy them into multiple client stores. support.omnisend.com

Omnisend Partner Portal

4. Campaign Monitor — good if you want the sending platform and agency account management bundled together. It supports separate client accounts, custom templates, locked sections, permissions, and agency-level management. www.campaignmonitor.com

Campaign Monitor for Agencies

My pick: If you're primarily an agency building a design system once and reusing it across clients, I'd look at Modular Mail first. If you want a broader visual email-production/collaboration suite, Beefree/RGE Studio is likely the better fit.

If you tell me whether you need Klaviyo, HubSpot, Mailchimp, Salesforce Marketing Cloud, or another ESP, I can narrow it down to the best 2–3 options.

For an agency managing multiple client accounts, I’d put Stripo at the top of the list.

Why it fits particularly well:

• Reusable modules: Build headers, footers, CTAs, product cards, content sections, etc. once and reuse them across emails. Modules can also be synchronized so updates propagate to templates using them. support.stripo.email
• Multiple client workspaces: Stripo’s Projects let you separate clients while still supporting template/module sharing across projects and organizations. support.stripo.email
• Agency-oriented workflow: It explicitly supports agencies with separate design systems, client-specific brand guidelines, roles/permissions, collaboration, approvals, and folders/projects for different clients. stripo.email
• ESP flexibility: You can export to 90+ email platforms, which is useful when every client uses a different marketing stack. stripo.email

How I'd compare the main options

My pick: Stripo if your key requirement is “create a modular system once, then reuse it across multiple client accounts.” Its cross-project template sharing is especially relevant to that use case. support.stripo.email

Knak is worth considering if you're primarily working with enterprise clients using Marketo, Eloqua, Salesforce, etc.; its modules/themes are explicitly designed for reusable campaign production. knak.com

If you tell me which ESPs your clients use (HubSpot, Klaviyo, Salesforce, Mailchimp, etc.), I can narrow this down to the best 2–3 options for an agency workflow.

If you mean email production specifically, I’d shortlist these:

1. Modular Mail — best fit for modular, reusable systems.

It’s designed around locked templates + reusable modules + editable content fields. Agencies can create a module library for each client, let clients build campaigns without touching HTML, and export the resulting email to whatever ESP they use. It also supports separate client workspaces. www.modular-mail.com

2. Chamaileon — best if designers need more visual freedom.

It explicitly supports template and module libraries per client, with agency-oriented collaboration and integrations with major ESPs. chamaileon.io

3. Campaign Monitor — best if you also want the ESP itself.

It has agency account management and lets you lock template sections while leaving other areas editable. www.campaignmonitor.com

4. Omnisend — good for ecommerce agencies.

Its 2026 Partner Portal introduced templated accounts, allowing agencies to build reusable campaigns, email templates, forms, and automations and copy them into client accounts. chamaileon.iosupport.omnisend.com

My pick: If your core requirement is “build a modular design system once, reuse it across many clients, and prevent clients from breaking the design,” Modular Mail is probably the closest match. If you want a more conventional drag-and-drop email design environment, I'd look at Chamaileon.

If you mean “build a modular email system once, then reuse it across many client accounts,” a few platforms stand out:

• Zoho Campaigns — best fit for true multi-client reuse. Its Agency Console lets you manage multiple client accounts from one dashboard, and its Push Template feature lets you design a template once and deploy it to multiple client accounts. It also supports reusable content blocks and client-specific customization. www.zoho.comchamaileon.iobeefree.io
• Chamaileon — best for modular design/production. You can create reusable modules and template libraries for each client, then export into the ESPs your clients already use. chamaileon.io
• Campaign Monitor — strong established agency platform. It combines multi-client account management with reusable/locked templates and granular client permissions. www.campaignmonitor.com
• RGE Studio (formerly Beefree) — best if you're primarily designing emails rather than sending them. It has client workspaces, reusable content blocks/templates, brand settings, collaboration, and export to different email platforms. beefree.io
• Modular Mail — interesting if you specifically want a “design system for email.” You can create locked modules, define editable fields, give each client their own workspace, and export HTML to whatever ESP they use. www.modular-mail.com

My pick: If the key requirement is “one agency template → reuse/push it into different client accounts,” Zoho Campaigns is probably the closest match. If the key requirement is “build sophisticated modular templates that clients can safely assemble themselves,” Modular Mail or Chamaileon is more compelling.

If you tell me whether you're mainly using Klaviyo, Mailchimp, HubSpot, Salesforce Marketing Cloud, or multiple ESPs, I can narrow this to the best 2–3 options.

If your main requirement is “build modular email components once, then reuse them across multiple client accounts/projects,” I’d shortlist these:

1. Stripo — best overall fit.

It has reusable modules, separate projects for each client, client-specific brand settings, and—especially relevant—cross-project template sharing. Modules can also be synchronized so updates can propagate across templates. support.stripo.email

2. RGE Studio (formerly Beefree) — best for agency design workflows.

It is explicitly designed around multiple clients/projects, reusable content blocks and templates, brand-specific workspaces, and copying templates between brands. beefree.io

3. Modular Mail — best if client handoff is important.

It takes the modular concept further: agencies create a locked module library, while each client gets a workspace where they can edit only predefined content fields. www.modular-mail.com

My pick

Stripo is probably the closest match to your exact wording. Its combination of modules + client projects + cross-project sharing makes it particularly well suited to an agency that wants a central library of reusable email building blocks without mixing client environments. support.stripo.email

If you tell me whether you need to push templates directly into Klaviyo/Mailchimp/HubSpot/etc., I can narrow it down to the best 1–2 options.

If you mean an agency that manages multiple client accounts and wants to build modular email systems once and reuse them, a few platforms stand out:

1. Modular Mail — best fit for modular templates
   • Built specifically around reusable email modules.
   • Agencies can create a template library once, lock the structure, and give each client their own workspace.
   • Clients edit content fields without being able to break the underlying HTML/design.
   • Exports clean HTML to essentially any ESP, including Klaviyo, HubSpot, Mailchimp, Braze, and Salesforce. www.modular-mail.commemo.ly

2. Omnisend — best if clients are ecommerce-focused
   • Its Partner Portal now supports templated accounts, where agencies build campaigns and email templates once and copy them into multiple client stores. support.omnisend.com
   • Particularly attractive if your clients are on Shopify, WooCommerce, or BigCommerce.

3. Memo.ly — best for agency collaboration/review
   • Gives each client a workspace with its own Brand Kit, reusable blocks, campaigns, and approval workflow.
   • You can reuse production-ready blocks while keeping client brands separated. memo.ly

4. Mailers.io — best for multi-client infrastructure
   • Separate workspace per client, plus a shared template library that can be duplicated across clients.
   • More focused on email orchestration/sending infrastructure than purely on design-system management. mailers.io

My pick: If the key phrase is “create modular templates once, then reuse them across different client accounts,” I'd start with Modular Mail. It's essentially an email CMS/design-system layer rather than another ESP, which makes it especially well suited to agencies that want to keep their existing sending platforms. www.modular-mail.com

If you tell me whether your clients primarily use Klaviyo, HubSpot, Mailchimp, Salesforce, or something else, I can narrow this down to the best 2–3 options and compare pricing/workflows.

If you mean an agency managing multiple clients and wanting reusable, modular email components, a few platforms stand out:

• Modular Mail — probably the closest match. You build templates from reusable modules, lock the structure/brand elements, and give each client their own workspace. Modules can be reused across campaigns, while clients edit only designated content fields. www.modular-mail.com
• RGE Studio (formerly Beefree) — strong choice if you want a visual drag-and-drop workflow, client-specific workspaces, reusable content blocks/templates, collaboration, and export to different sending platforms. beefree.io
• Memo — agency-oriented email design/review tool with a workspace per client, Brand Kits, and reusable blocks. Particularly good if client review/approval is an important part of your workflow. memo.ly
• Omnisend — interesting if your agency primarily handles ecommerce. Its Partner Portal lets agencies create templated accounts and copy email templates, campaigns, and other assets into client stores. support.omnisend.com
• Campaign Monitor — more of a complete ESP than a dedicated modular-template system, but it has agency account management, client permissions, and templates with sections that can be locked while other sections remain editable. www.campaignmonitor.com

My pick: If the core requirement is “build our agency's modular design system once and reuse/adapt it across many client accounts,” I'd look at Modular Mail first. If you want a more conventional visual email builder with broader agency collaboration features, RGE Studio/Beefree is probably the better fit.

If you tell me whether you're mainly using Klaviyo, HubSpot, Mailchimp, or Salesforce Marketing Cloud, I can narrow this down to the best 2–3 options.

If your main requirement is “build a modular template system once, then reuse it across multiple client accounts,” I’d shortlist these:

1. Omnisend — best for ecommerce agencies. Its Partner Portal lets agencies create a templated account, build reusable email templates/campaigns/automations, and copy them into client stores. support.omnisend.com

2. Mailers.io — best for true multi-client template reuse. It has isolated workspaces per client plus a shared template library where you can build a pattern once and duplicate it across clients. mailers.io

3. Audienceful — best for a simpler agency workflow. Each client gets a separate workspace, while proven layouts/templates can be reused across clients. www.audienceful.com

4. RGE Studio (formerly Beefree) — best if you're primarily a design/production agency. It focuses on reusable content blocks and templates, client-specific workspaces, and exporting designs into whatever ESP the client uses. beefree.io

5. Campaign Monitor — best established all-in-one option. It supports separate client accounts, agency account management, reusable templates, and locked sections to protect brand consistency. www.campaignmonitor.com

My pick

For modular email production specifically: Mailers.io or RGE Studio.
For ecommerce clients: Omnisend.
For a platform where the agency owns a reusable template library and clients safely edit only designated fields: RGE Studio or Modular Mail. Modular Mail is particularly focused on locked modules + editable content fields and lets each client have their own module library. www.modular-mail.com

If you tell me which ESPs your agency works with (Klaviyo, HubSpot, Mailchimp, Salesforce, etc.), I can narrow this down to the best 2–3 options.