Mailgun alternatives

The highest-scoring alternative to Mailgun is Resend at 89/100 on the AgentReady, against 58/100 for Mailgun.

Score	Alternative	Compare
89	Resend	Mailgun vs Resend
84	Agentmail	Mailgun vs Agentmail
69	Nylas	Mailgun vs Nylas
66	Loops	Mailgun vs Loops
66	Mailtrap	Mailgun vs Mailtrap
62	ZeroBounce	Mailgun vs ZeroBounce
56	Ahasend	Mailgun vs Ahasend
55	Pipedrive	-
54	SuperTokens	-
53	Sendgrid	-
47	Mailersend	-
47	Twilio	-
43	Postmark	-
34	Pulsemcp	-
33	Brevo	-
26	Plunk	-

What Resend does that Mailgun does not

Resend passes public docs discoverable, llms.txt published, llms-full.txt / full agent docs, structured api reference, openapi / spec quality, request examples provided, response examples provided, limits / constraints documented, no mandatory sales call, programmatic credential creation, cli available, structured, predictable output, idempotency support, and Mailgun fails them. That is the whole of the gap between the two scores, so if none of those matter to your agent the ranking above overstates the difference.

Why people look for an alternative

Mailgun fails public docs discoverable, llms.txt published, llms-full.txt / full agent docs, structured api reference, openapi / spec quality, request examples provided, response examples provided, errors and status codes documented, limits / constraints documented, no mandatory sales call, programmatic credential creation, cli available, structured, predictable output, machine-readable errors, retry behavior documented, idempotency support, rate-limit behavior predictable. Each one is a place an unattended run stops, which is usually what sends someone looking in the first place.

Where Mailgun loses the points

Pillar	Mailgun	What it measures
Discover	73	Can an agent find it at all: sitemap, robots, structured data.
Understand	31	Is there a spec, an llms.txt, a machine-readable description.
Adopt	75	Signup, keys, SDKs, and whether a human has to be involved.
Operate	53	Rate-limit headers, errors, status, and behaviour under load.

Mailgun is weakest on understand at 31/100. Without a spec an agent has to guess at endpoints, and it guesses wrong. If that is the part your agent depends on, take the ranking above seriously; if it is not, Mailgun may still be the right pick.

What an agent runs into with Mailgun

These are the findings from the last audit on 2026-08-22. Each one is a place unattended software stops, which is the practical reason to look at the list above.

Make docs reachable without auth or navigation gymnastics.
Publish an OpenAPI spec so agents can generate a client.
Flesh out the OpenAPI: paths, schemas, and descriptions.
Document error responses as an enum in your OpenAPI.
Let agents create API keys programmatically.
Return X-RateLimit / Retry-After headers so agents pace themselves.
Add /llms.txt so agents can find and read your capabilities.
Publish an AGENTS.md or llms-full.txt with full agent context.

What this category actually supports

Across the 17 products scored in Transactional Email, send transactional email is offered by 71%, send bulk / marketing email is offered by 53%, receive / inbound email is offered by 12%, verify an email address is offered by 12%. Anything under half is a gap you should expect to fill yourself whichever one you pick.

An agent can get this list directly: resolve("alternative to Mailgun") over the MCP server, or GET /v1/categories/email.