Mailpit alternative: GrabMail vs Mailpit and MailHog

At a glance

Fourteen rows, several of which read “not applicable” for a tool that lives on your own host. Every Mailpit cell is what its documentation, README and runtime-options page said on 2 September 2026; every GrabMail cell is read from the constants the service enforces.

Checked 2 September 2026. Mailpit’s defaults are quoted from its runtime options: 500 most recent messages kept, a temporary database deleted on exit, a 50 MB message limit. MailHog’s status is inferred from its repository dates, which are quoted; the project carries no deprecation notice.

What Mailpit does well

Mailpit is the tool to run next to your application while you build it. Four things it does that GrabMail does not:

• It catches everything you send, locally. Point your app at port 1025 and every message lands in the web inbox on 8025 — passwords resets, invoices, the lot — without a single one reaching a real address. GrabMail never sees your outbound mail.
• It tests the message, not just the delivery. HTML compatibility checks, a link checker, SpamAssassin scoring, screenshots, tagging. GrabMail hands you the message and stops.
• Chaos. Since version 1.20 it can inject SMTP failures at chosen stages with chosen probabilities, to prove your application copes when the mail server does not. Nothing hosted offers that.
• It is yours. MIT-licensed, a single binary, two hundred to three hundred messages a second, no vendor, no account, no internet needed. GrabMail is somebody else’s server, and everything on it is public.

Where GrabMail is different

GrabMail does the one thing a local SMTP catcher cannot: exist on the internet, with addresses other people’s servers can deliver to.

• Real inbound mail. A test signs up to a third-party service and that service sends a code — to GitHub, to Stripe, to whatever you are integrating with, the address has to be real. run-42@grabmail.io is real, has an MX record, and its mail is readable with a keyless GET.
• Nothing to run, nothing to expose. Making Mailpit receive from the internet means a public host, an MX record and a firewall rule, and its documentation does not position it for that. GrabMail is already there; a CI runner needs only outbound HTTPS.
• Your own domain as a catch-all, hosted. One MX record at smtp.grabmail.io and every address on the domain receives from anywhere, kept 5 days, no daemon of yours involved.
• An MCP server for agents. An agent that must sign itself up somewhere cannot use a local SMTP catcher at all. GrabMail’s server at https://grabmail.io/mcp gives it an inbox and a blocking wait_for_message of up to 25 seconds, with no key.

Price, side by side

There is nothing to price at Mailpit: it is free software, and its cost is the host you run it on. GrabMail’s only paid plan buys access to a pool of domains kept off the disposable-mail blocklists; everything in the table above stays free.

As published on 2 September 2026. GrabMail’s pricing page has the full grid.

For developers: reading a mailbox

The two APIs read different mail, so here is the one that reads inbound mail from the outside world. This reads a GrabMail mailbox with no header, no key and no account:

$ curl -sG https://grabmail.io/api/v1/mailbox --data-urlencode "address=anything@grabmail.io" | jq '{count, alias}'

Mailpit’s equivalent is GET http://localhost:8025/api/v1/messages on your own instance, listing what your application sent to it — the right call for asserting your app produced the right message. Reading what a third party sent to a test user is GrabMail’s job; the reference is three endpoints, and the GitHub Actions guide shows both kinds of test in one workflow.

In CI the two sit side by side: Mailpit as a service container on 1025 for the application’s own mail, GrabMail addresses for the sign-ups the suite performs against real services. Neither needs a secret.

For AI agents

Mailpit publishes no MCP server and no llms.txt, and a local SMTP catcher is not something an agent signing up to a website can use. GrabMail’s server at https://grabmail.io/mcp gives an agent an inbox with no key: create_inbox, a blocking wait_for_message of up to 25 seconds, read_message.

Email for AI agents covers the four-call loop and the guard rails; the client guide has the configuration for Claude, Cursor and five others.

Switching from Mailpit or MailHog

From MailHog, switch to Mailpit — that is the maintained replacement for the same job. From either to GrabMail only for the tests that receive:

1. Replace MailHog with Mailpit for capture. Same idea, same ports, a maintained project: docker run -p 8025:8025 -p 1025:1025 axllent/mailpit. Nothing about that involves GrabMail.
2. Find the tests that talk to the outside. A test that registers with a real third-party service and waits for its mail cannot be served by a local catcher. Give it run-{id}@grabmail.io, or an address on a domain you point at smtp.grabmail.io.
3. Read it with a GET. /api/v1/mailbox?address=… every second with a deadline; the Playwright guide has the loop. No token, no service container.
4. Keep Mailpit for everything else. Templates, links, spam scores, failure injection: that is its job, and GrabMail cannot do any of it.

Which one, for what

The honest split is by direction:

When to stay with Mailpit

Three situations where GrabMail is the wrong tool:

• Your tests check what you send. GrabMail cannot see your application’s outbound mail at all. That is Mailpit’s whole purpose.
• Your mail must not leave the building. A local catcher keeps every message on your host; every GrabMail mailbox is public on the internet.
• You test failure. Chaos mode, relay to a real server, forwarding rules: features of a tool you run, with no hosted equivalent here.

Questions