Agencies and consultancies face an email tooling problem solo marketers don't: every client account adds complexity, every handoff invites mistakes, and the wrong platform turns a routine retainer into a support burden. This review is shaped around that reality. It looks at six email platforms agencies actually use day-to-day, then walks through the selection criteria that matter when you're sending on behalf of multiple brands rather than one.
Across every tool below, one practice separates agencies that scale from those that stay stuck cleaning up bounces: verify each client's list before the first send. Free email checker handles quick sample tests; for full client onboarding, run imports through the email verification software so you inherit clean data, not someone else's mess. Both are part of the same Proofy account — see pay-as-you-go pricing for agency-scale volume tiers.
Selection Criteria That Matter for Agencies
Multi-Client Account Management
Some platforms charge per workspace. Some let you spin up unlimited sub-accounts under one agency master. The difference compounds fast when you sign your fifth or tenth client. Before signing anything, ask the vendor directly: "What does my bill look like at ten client accounts versus three?" The answers vary by an order of magnitude.
White-Label and Reporting
If your client sees a screenshot of the platform, your brand should be on it - not the vendor's. Decent white-label support starts with custom report headers and ends with full domain masking. Most platforms charge a premium for it; the few that include it at the agency tier are worth a closer look.
Pricing Model Predictability
Per-contact pricing is straightforward but penalizes you when clients import old lists. Pay-per-send rewards volume but punishes infrequent campaigns. Hybrid plans exist, but read the fine print on add-ons - dedicated IPs, additional users, and API call limits often arrive as separate line items.
Cross-Platform Access
Account managers check campaigns on phones at airport gates. The mobile experience isn't optional anymore. Test the platform's mobile app, not just the responsive web view, before committing.
Deliverability and Authentication Help
Setting up SPF, DKIM, and DMARC for each new client is now table stakes. A platform that walks the client through their DNS panel - or handles it directly via API - saves hours per onboarding. With Gmail and Yahoo enforcing authentication for bulk senders, this isn't a nice-to-have. Our guide on email deliverability practices covers the full setup checklist.
Six Platforms Worth Reviewing
Brevo
Strong fit for agencies running many small client accounts. Pricing by sends rather than contacts means a client with 50,000 inactive addresses costs the same as one with 500 active ones, which can save real money on cleanup-stage clients. Includes transactional email, SMS, and a light CRM, so an agency can offer broader retainers without bolting on three tools.
SendPulse
Multichannel platform spanning email, SMS, web push, and chatbots. The free tier covers 500 subscribers per workspace, which works for early-stage clients. Automation is more limited than Brevo's, but the multichannel mix wins where the client wants a unified messaging strategy without buying additional vendors.
MailerLite
Plain interface, generous free tier (1,000 subscribers, 12,000 monthly emails), and lower pricing curve than Mailchimp at every step. Less suited to complex automation but well-suited to small-business clients who want their emails to look clean without micromanagement. Proofy has a native MailerLite integration that simplifies list hygiene at scale.
Mailchimp
The most common request when a small-business client says "we use email marketing." Familiarity is the strongest feature - onboarding the client back into their own dashboard takes minutes. Pricing is the weakest: per-contact billing escalates fast, and recent gates moved older free features into paid tiers. Still a default choice for clients who insist on it.
AWeber
Long-standing autoresponder platform. Unusual for offering unlimited automations on its free tier (500 subscribers). Where it shines for agencies is on stability - fewer interface changes, fewer surprise feature reshuffles, and per-list pricing that's easy to explain to clients. Less suited to advanced segmentation than Brevo or HubSpot.
HubSpot
Email is one slice of the broader Marketing Hub. The value for an agency comes from the bundled CRM, landing pages, and lead scoring - clients with $50k+ retainers often want that integrated story rather than five separate tools. Cost climbs quickly above 2,000 contacts on paid tiers, so it suits mid-market clients rather than scrappy small businesses. For agencies formalizing mid-market client engagements, how advertising RFPs work covers the framework for scoping campaigns and aligning on budget before platform selection.
How to Choose for a Specific Client
Don't apply one platform to every account. The trade-off between simplicity and capability is real, and the right answer depends on the client's revenue model:
- Small-business retainers, $2-5k a month, sending newsletters and basic promotions ? MailerLite or Brevo.
- Ecommerce clients with Shopify and serious revenue at stake ? Klaviyo or Drip (covered separately).
- B2B clients with sales-cycle nurture flows ? HubSpot or ActiveCampaign.
- Clients who insist on Mailchimp because "we already use it" ? use it well, charge appropriately for the migration if it ever happens.
Common Mistakes Agencies Make With Email Tools
- Defaulting to the agency's preferred tool, regardless of client fit. The platform should match the client's business model, not your account manager's comfort zone.
- Skipping list cleanup at onboarding. Inheriting a dirty list and sending from it tanks the new sender domain immediately. Verify before the first campaign.
- Underestimating sub-account billing. Per-workspace pricing looks reasonable at three clients and brutal at ten. Run the math at projected volume before signing.
- Forgetting to bill for deliverability setup. Configuring SPF, DKIM, and DMARC for each client is real work. Scope it explicitly in the engagement letter or it becomes free labor.
- Treating Mailchimp as the universal answer. It works for many clients, but assuming it works for all of them costs you on the few who need automation or ecommerce depth.
Further reading: see our piece on how advertising RFPs work for agencies for the deeper context.
FAQ
Should agencies use one platform for all clients?
Rarely. A reasonable stack for a mid-sized agency is two to three platforms, picked to cover small business (MailerLite or Brevo), ecommerce (Klaviyo or Drip), and mid-market B2B (HubSpot). Trying to force-fit one tool across all client types creates retention problems on both ends.
How do agencies handle email verification at scale?
API integration is the standard answer. New signups from any client account get validated in real time, and bulk verifications run before each major send. The cost per address drops at volume, and the work doesn't scale linearly with client count.
What's the difference between transactional and marketing email tools?
Transactional email sends triggered messages - order confirmations, password resets, receipts. Marketing email sends broadcasts and automated sequences. Brevo, SendinBlue (now Brevo), and SendGrid handle both; tools like Mailchimp and Constant Contact focus on marketing. For ecommerce clients especially, the distinction matters - transactional volumes are often 10x marketing volumes.
How do I migrate a client between platforms?
Subscriber export and re-import is the easy part. The harder parts are: rebuilding automation logic from scratch, warming up the new sending domain so deliverability doesn't crash, and historical reporting that doesn't transfer between vendors. Plan four weeks for a full migration of an active client, not one.
Does white-label reporting matter for retention?
It matters more than agencies usually credit. Clients who see your branding consistently feel like they're paying for a service, not renting access to a tool they could buy themselves. Vendors charge for it because they know.
Bottom Line
Pick the email platform that fits the client, not the agency. Build a small core stack - two or three platforms that cover most client situations - and treat anything beyond that as a one-off decision. Verify lists at onboarding without exception. And revisit each tool annually: the platform that was right for a client last year may have rebranded, repriced, or pivoted by now. Email tooling moves; your process should too.
