Email marketing platform for an agency managing several clients' accounts

For an agency managing several clients’ email marketing, I’d shortlist:

• Zoho Campaigns Agency Edition — strongest fit if you want a purpose-built agency console: manage multiple client accounts, set permissions, collaborate with clients, and centrally reuse templates. (zoho.com)
• MailerLite — a straightforward option for smaller agencies: one login to switch between separate client accounts, with each client’s subscribers, campaigns, automations, and templates kept separate. (mailerlite.com)
• Mailchimp & Co — worth considering if your clients already use Mailchimp; it lets agencies connect to and switch between client accounts without sharing logins. (mailchimp.com)
• Klaviyo — consider it for ecommerce clients, especially if they need a separate account per store. (help.klaviyo.com)

My default pick: Zoho Campaigns if centralized multi-client management is the main priority; MailerLite if you want a simpler setup. Keep each client’s audience in its own account rather than combining client lists.

If you share how many clients you manage and whether they’re mostly ecommerce or general businesses, I can narrow it down.

Campaign Monitor is the strongest general fit for a multi-client agency, with Brevo, Moosend, and ActiveCampaign as the main alternatives depending on budget and client type. Most of the sources below are vendor-affiliated comparison blogs, and their prices conflict, so check current pricing directly before you commit.

Top picks

• Campaign Monitor (best overall for agencies): One roundup calls it the only platform in this roundup whose standard pricing page lists client sub-accounts, private labeling, and a billing system that charges each client with your markup added. Another review says its agency dashboard, white-label reporting, granular permissions, and template locking make multi-client work seamless. The trade-off is that its starting price is not published, so you'll need to request a quote.
• Brevo (budget option): It offers a Corporate solution that lets agencies create sub-accounts, enabling them to manage multiple brands under a single umbrella account. Sub-accounts are limited to the higher tier, so check which plan includes them.
• Moosend (lowest cost per client): It offers sub-accounts, flexible billing, and client management tools. One roundup puts it at about $48 a month per 5,000-contact client, while another lists a Pro plan at $7/month billed annually at 500 subscribers.
• ActiveCampaign (best for automation-heavy retainers): Its agency structure uses separate accounts, and one review notes that the Plus plan, which you need for CRM and lead scoring, is $49/month for 1,000 contacts. Another source says sophisticated multi-client features such as custom roles, advanced reporting, and white labelling are gated behind Enterprise pricing.

Platforms for specific client types

• Klaviyo: Best if most of your clients run Shopify or WooCommerce stores. One roundup describes free plans up to 250 contacts per client.
• Mailchimp: Simplest if clients already have accounts. Its sub-account model is different: it has no sub-account structure, and you join Mailchimp & Co to switch between client accounts.
• GoHighLevel or DM Champ: These are better if you also want to resell email with CRM, funnels, and SMS. One source says GoHighLevel offers unlimited client sub-accounts at $297 per month.

How to decide

1. Ownership model: Decide whether you'll hold each client's account under your master login, or whether clients own their accounts and you just get access. Sub-accounts with consolidated billing matter most if you resell the service.
2. Billing: Per-contact pricing can get expensive across many lists. Per-client flat pricing or per-send pricing is often cheaper for agencies with many small lists.
3. White-labeling: Only some tools let you brand the dashboard for clients. Check this if clients see the platform directly.
4. Deliverability isolation: Make sure each client's sending domain and reputation are kept separate, so one client's problems don't affect the others.

If you tell me how many clients you manage, their typical list sizes, and whether they're e-commerce or service businesses, I can narrow this to one or two options.

For agencies managing multiple clients, selecting an email marketing platform requires features that prioritize operational efficiency, data isolation, and professional reporting rather than just standard marketing tools.

The following platforms are highly recommended because they offer specific "agency-first" features, such as multi-tenant sub-accounts, white-labeling, and centralized billing.

Top Recommendations for Agencies

What to Look for in an Agency-Grade Platform

When evaluating these or other tools, ensure they meet these non-negotiable requirements for agency operations:

• Multi-Client Management (Sub-accounts): You should be able to manage all client accounts from a single "Master" dashboard. Avoid platforms that require you to log out and back into separate accounts, as this creates significant operational friction.
• Data & Deliverability Isolation: Each client must have their own separate list and sending reputation. This prevents "cross-client contamination," where one client’s poor deliverability (e.g., high bounce rates or spam complaints) negatively impacts the performance of your other clients.
• White-Label Reporting: You need the ability to provide reports that represent your agency’s brand. Platforms that plaster their own logo on every client-facing report can undermine your agency’s positioning.
• Role-Based Access Control: You should be able to define what each person (team member or client) can see or do. For example, some clients may want to view reports but not edit automation flows, while your team members may need full access to specific client sub-accounts.
• Scalable Billing: Look for platforms that allow you to manage billing at the client level or offer agency partner programs with discounted pricing, which protects your margins as you grow your client base.

A Note on "Creator" Tools

Platforms like beehiiv, Kit, or Substack are often popular for individual creators but are generally not recommended for agencies. They lack the multi-tenant architecture, robust permission controls, and dedicated deliverability features necessary to manage 10–30+ different clients effectively.

For an agency managing several clients, Brevo is a strong starting point: its Agency Partner Program lets you switch between client-owned accounts and manage them from one partner login. Clients can grant your team access, while each client retains their own account. ¹³

Other good fits, depending on your workflow:

• Mailjet — worth considering if you want client subaccounts under one master account, with isolated client data and reporting, plus a single bill. ⁵
• Mailchimp & Co — useful if your clients already use Mailchimp; it connects their accounts so you can manage them from one login, while billing and account data remain separate. ⁸¹⁵
• Emma — consider it if white-labeling and a centralized dashboard for separate client accounts are priorities. ¹³

Quick pick: Brevo for managing client-owned accounts; Mailjet for centralized subaccounts and billing; Mailchimp & Co for clients already on Mailchimp. Check current plan limits and pricing against your client count and contact volumes before committing.