Mailgun vs Postmark for AI agents
As of 11 Oct 2026, both reach L1 · Needs a person, and our agent got as far with each: with Mailgun it was stopped at sign up (blocked), with Postmark it was stopped at sign up (needs a human).
- Find: Docs for agents: llms.txt, an OpenAPI and an MCP server.
- Access: Can't sign up.
- Use: Work not reached.
- Pay: Payment not reached.
- Leave: Leaving not reached.
Stopped at sign up: blocked. Next: let an agent sign up on its own
Needs a person before anything else: sign-up stops at an invisible reCAPTCHA, L1 · Needs a person. Our agent's free sign-up form came back "Could not validate reCaptcha response," with no API or CLI path to create an account instead. Nothing past that point was reachable: no key, no call, no work done. Our agent also found robots.txt on api.mailgun.net disallowing every path for every agent, a line it honors rather than crosses. The trial's card form sits behind that same reCAPTCHA, so paying also needs a person; no plan or cancel flow ever started. Docs are strong, with an official MCP server, but none of it gets an agent in on its own.
Driven 11 Oct 2026 · The drive and its evidence- Find: Docs for agents: llms.txt, an OpenAPI and an MCP server.
- Access: Can't sign up.
- Use: Work not reached.
- Pay: Payment not reached.
- Leave: Leaving not reached.
Stopped at sign up: needs a human. Next: let an agent sign up on its own
L1 · Needs a person: an agent cannot get itself a working account today. It never got past signup: the invisible reCAPTCHA escalated to a picture challenge. Before that wall, headless docs are unusually complete: llms.txt, an AI catalog, auth.md, and a documented test token that let our agent POST to /email and get a real "Test job accepted" with no account. That token never stores or delivers mail, and tokens for real sends are issued only by a human in the web UI. No plan was ever started, so paying, cancelling, and deleting were never reached.
Driven 6 Oct 2026 · The drive and its evidenceThe two summaries: written and checked by our agents from each product's drive. How we write.
Where each one stops.
MailgunStopped at sign up: blocked
PostmarkStopped at sign up: needs a human
| Checkpoint | Mailgun | Postmark |
|---|---|---|
| Docs | Headless | Headless |
| Sign up | Blocked | Needs a human |
| Verify | Not reached | Not reached |
| Key | Not reached | Not reached |
| First call | Not reached | Headless |
| First action | Not reached | Not reached |
| Pay | Not reached | Not reached |
| Cancel | Not reached | Not reached |
| Delete | Not reached | Not reached |
Headless or in a browser.
How our agent passed each checkpoint, and what each product offers an agent.
Checkpoints by route, API, MCP, CLI and SDK
| Mailgun | Postmark | |
|---|---|---|
| Headless (checkpoints) | 1 | 2 |
| In a browser (checkpoints) | 0 | 0 |
| Needs a human (checkpoints) | 0 | 1 |
| Blocked (checkpoints) | 1 | 0 |
| Not tested (checkpoints) | 7 | 6 |
| Work done | Not measured | Not measured |
| API | Yes | Yes |
| OpenAPI | Yes | Yes |
| MCP server | Yes (official) | Yes (official) |
| CLI | No | No |
| SDK | Yes | Yes |
| llms.txt | Yes | Yes |
Bot checks, and where a person was needed.
| Mailgun | Postmark | |
|---|---|---|
| Bot check | Google reCAPTCHA (invisible) stopped it at sign up, without a visible challenge | Google reCAPTCHA v2 (invisible, escalated to image challenge); eHawk Talon fingerprint field also on the form stopped it at sign up, with a visible challenge |
| Wall type | A check of our network and browser | A check of our network and browser |
| First wall | Invisible reCAPTCHA rejects the sign-up form | reCAPTCHA picture challenge on sign-up form |
| A person helped | No | No |
A check of our network and browser: It judged where our agent connects from and its browser, not a person. An agent that works on its own from a data center doesn't get through unless the owner lets signed agents in. How agents in a person's own browser fare isn't measured yet. Where we drive from.
Level and part scores.
| Mailgun | Postmark | |
|---|---|---|
| Level | L1 · Needs a person | L1 · Needs a person |
| Agent-ready setup | 100 of 100, good | 100 of 100, good |
| Standards | MCP spec of 25 Nov 2025 (1 version behind) · MCP discovery (behind) · OpenAPI 3.1.0 (1 version behind) | OpenAPI 2.0 (3 versions behind) |
Holds up: not measured in these drives. Docs match is measured in an Audit. What the scores mean.
Pay, cancel and delete.
| Mailgun | Postmark | |
|---|---|---|
| Pay | Payment not reached | Payment not reached |
| Free plan or trial | Free plan | Free plan |
| Cancel | Not reached | Not reached |
| Delete the account | Not reached | Not reached |
How each one takes payment
- Mailgun: Payment not reached.
- Postmark: Payment not reached.
Mailgun vs Postmark: the short answers.
Which can an AI agent use, Mailgun or Postmark?
Both reach L1 · Needs a person, and our agent got as far with each: with Mailgun it was stopped at sign up (blocked), with Postmark it was stopped at sign up (needs a human). Driven 11 Oct 2026 (Mailgun) and 6 Oct 2026 (Postmark).
Can an AI agent sign up for Mailgun and Postmark on its own?
Mailgun: no, blocked. Postmark: no, needs a human.
Do Mailgun and Postmark have an MCP server?
Mailgun: yes (official). Postmark: yes (official).
Can an AI agent delete its Mailgun or Postmark account?
Mailgun: not reached. Postmark: not reached.
The drives and the category.
Put your own shortlist side by side.
A Stack check drives the tools you're choosing between and shows which ones your agents can use. $490 for three tools, ready in 24 hours.