Comparison

Choosing an email API in 2026

Postmark, Resend, Brevo and Charlie — where each one actually fits, from someone who builds on this stuff.

Every email API sends email. They differ on four things that matter once you're past the demo: how you're charged, whether marketing mail is allowed at all, where the data lives, and how much the platform protects you from your own mistakes. Here's an honest read, including where Charlie is the wrong answer.

Postmark

The reference for transactional deliverability. A decade of reputation, obsessive uptime culture, excellent support. Priced per send — roughly $15 per 10,000, about $55 at 50,000.

Fits when transactional mail is critical and you want the safest possible pair of hands. Doesn't fit if you need marketing and transactional in one place — Postmark deliberately separates streams and is strict about what counts as bulk. US-hosted, which matters for some EU procurement.

Resend

The best developer experience of the group — clean SDKs, React Email, fast setup. Generous free tier, then per-send pricing in the same band as Postmark.

Fits teams who value DX above everything and are happy on US infrastructure. Doesn't fit if you need EU data residency, or a full marketing feature set rather than good transactional plus broadcasts.

Brevo (formerly Sendinblue)

French, so genuinely EU, and a full marketing suite — campaigns, automations, CRM, SMS. Priced by sends with a free tier, and cheap at low volume.

Fits a business that wants a marketing platform with an API attached. Doesn't fit developers who want an API-first product — the API is real but the centre of gravity is the dashboard, and deliverability on shared low-tier infrastructure is variable.

Charlie

Ours, so read this with appropriate suspicion. EU-hosted on infrastructure we own rather than resell. Transactional and marketing through the same authenticated pipe. Priced per send: free at 50/day, €19 for 20,000, €49 for 50,000, quoted above that.

Two things are genuinely different. First, an MCP server — your agent can operate the platform as tools rather than you writing a client, which matters if AI is already part of how you work. Second, guardrails are enforced rather than documented: no sending from an unauthenticated domain, suppression on every path including transactional, one-click unsubscribe headers injected automatically, warmup and probation pools by default. If an autonomous process is sending your mail, that stops being paperwork and starts being the product.

Doesn't fit if you want a mature SDK for every language, a status page with years of history, or 24/7 phone support — we're small and honest about it. And if you run a Shopify store, the plans above don't apply; that's a separate product billed through Shopify.

The comparison that actually decides it

Prices are indicative and change; check before you commit. Note that we are not cheaper than the field at volume, and we don't try to be — competing on price attracts senders who burn shared IP reputation, which is the one asset a small platform cannot rebuild.

How to actually choose

• Transactional only, deliverability is existential: Postmark.
• You want the nicest DX and US hosting is fine: Resend.
• You want a marketing suite your marketing team will log into: Brevo.
• EU residency, one pipe for both kinds of mail, and an agent operating it: Charlie.

One last piece of advice that applies whichever you pick: send from a subdomain, start transactional, warm up slowly, and never let anything mail an address that bounced. The platform matters less than those four habits.