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Mailgun vs Postmark

Mailgun scores higher on the AgentReady, 58/100 against 43/100. They differ on 9 of the 41 signals. Which ones decides whether an agent can adopt them without a person watching.

What each one is

Mailgun. Transactional Email Delivery Service & API for Developers.

Postmark. Email delivery service for transactional emails focused on deliverability, speed, and developer experience

Where Mailgun is ahead

Mailgun passes mcp discoverable, and Postmark does not. That is discover, whether an agent can find the product at all without being told it exists.

It also holds adopt: agent-compatible signup flow, fast time to first request, copyable quickstart, official python sdk and mcp integration available. Postmark misses those.

And on operate, agent compatibility verified. Postmark misses it.

Where Postmark is ahead

Postmark passes llms.txt published, and Mailgun does not. That is discover, whether an agent can find the product at all without being told it exists.

It also holds adopt: no mandatory sales call. Mailgun misses it.

What neither does

Both fail public docs discoverable, 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, programmatic credential creation, cli available, structured, predictable output, machine-readable errors, retry behavior documented, idempotency support, rate-limit behavior predictable. If your agent needs any of those, you will be building it yourself either way.

Score, pillar by pillar

The AgentReady splits into four pillars, scored separately, because a product can be easy to find and still impossible to adopt.

Discover. Mailgun leads 73 to 67. Mailgun misses public docs discoverable, llms.txt published, llms-full.txt / full agent docs; Postmark misses public docs discoverable, llms-full.txt / full agent docs, mcp discoverable.

Understand. Both sit at 31/100 here. Mailgun misses structured api reference, openapi / spec quality, request examples provided, response examples provided, errors and status codes documented, limits / constraints documented; Postmark misses structured api reference, openapi / spec quality, request examples provided, response examples provided, errors and status codes documented, limits / constraints documented.

Adopt is whether an agent can get a key and make its first successful call without a human in the loop. Mailgun leads 75 to 40. Mailgun misses no mandatory sales call, programmatic credential creation, cli available; Postmark misses agent-compatible signup flow, programmatic credential creation, fast time to first request, copyable quickstart, official python sdk, cli available, mcp integration available.

Operate. Mailgun leads 53 to 35. Mailgun misses structured, predictable output, machine-readable errors, retry behavior documented, idempotency support, rate-limit behavior predictable; Postmark misses structured, predictable output, machine-readable errors, retry behavior documented, idempotency support, rate-limit behavior predictable, agent compatibility verified.

Pricing

Mailgun does not publish a machine-readable starting price and has a free tier. Postmark starts at $0/mo and has a free tier.

Signal by signal

Which to pick

Mailgun clears more of the signals an agent needs, so it is the safer default for unattended use. Full profiles: Mailgun and Postmark. Alternatives to each: Mailgun, Postmark.

An agent can fetch this as data: POST /v1/compare {"slugs": ["mailgun", "postmarkapp"]}