MailSlurp alternative: GrabMail vs MailSlurp

At a glance

Fourteen rows. Every MailSlurp cell is what its pricing page, documentation and llms.txt said on 2 September 2026; every GrabMail cell is read from the constants the service enforces. “Partly” means a paid tier, a cap, or a caveat the row cannot hold — the sections below say which.

Checked 2 September 2026. MailSlurp publishes monthly prices only; the annual toggle on its pricing page does not render a figure. The duration of the automatic expiry on free inboxes is not published either, so the table says “expire” without a number.

What MailSlurp does well

If email testing is a budgeted line and you want everything in one account, MailSlurp is the reference. Four things it does that GrabMail does not:

• It waits for you. waitForLatestEmail, waitForMatchingEmails and waitForNthEmail hold the request until the message exists, so a test has no polling loop to write and no sleep to tune. GrabMail’s REST API is polled; only its MCP server waits.
• It sends, and it has phone numbers. A flow that replies to a message, or one that verifies by SMS, can be tested end to end on the paid plans. GrabMail is receive-only and email-only, by design.
• Nine SDKs and a webhook on every plan. npm install mailslurp-client exists, in nine languages, with typed models; and an event arriving at an inbox can be posted to your endpoint even on Free. Here there is an OpenAPI document and a GET.
• A security story you can send to procurement. SOC 2 Type I, GDPR and CCPA badges, scoped agent roles, and an Enterprise tier with SAML, SCIM, audit logs and regional hosting. GrabMail publishes what it does not do and offers no SLA.

Where GrabMail is different

GrabMail is built for the cases MailSlurp’s Free plan caps out of and its paid plans price out: a job that must not hold a secret, a domain that must not cost anything, and an agent nobody is supervising.

• No key, so no secret store. A MailSlurp call needs x-api-key; a GrabMail call needs an address in the query string. A pull request from a fork, a snippet in a README and an agent on a stranger’s machine can all read a mailbox here without being trusted with anything.
• No monthly cap. MailSlurp Free stops at 500 inbound emails and 100 new inboxes a month, then asks for $49.99. A GrabMail address exists the moment mail arrives at it, on the public domains or on yours, with one read a second per address as the only limit — all month.
• Your own domain is free, and it is how you choose a name. MailSlurp assigns random local parts on its pooled domains and lets you choose a name only on a custom domain, which Free lacks and Pro meters. Here run-42@grabmail.io is yours by typing it, and any domain you point at smtp.grabmail.io becomes a catch-all inbox for nothing.
• Attachments and an MCP server on the free tier. MailSlurp delivers attachments from Pro upward; GrabMail takes 5 MB per message from the first day. Its MCP server needs no OAuth screen, which is what an agent working without a human in front of a browser needs.

Price, side by side

MailSlurp’s prices are monthly in US dollars, non-refundable except where the law requires, with usage-based overage above the included volumes. 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.

Prices as published on 2 September 2026. MailSlurp offers a card-backed trial on Pro and Team; its terms make fees non-refundable. GrabMail’s pricing page has the full grid.

For developers: reading a mailbox

The whole difference in one command. 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}'

The MailSlurp equivalent begins with an account, an API key and usually an SDK: create an inbox, then waitForLatestEmail(inboxId, timeout). That is more to set up and less to write in the test, because the wait is on the server. On GrabMail the wait is a loop with a deadline — twenty lines, shown in the Playwright, Python and Node.js guides — and there is nothing to install.

A CI detail worth knowing: MailSlurp’s key goes in a secret and the pipeline must be allowed to read it, which excludes pull requests from forks on most platforms. GrabMail needs no secret, so a fork’s pipeline can run the same email test. The GitHub Actions guide shows the workflow.

For AI agents

MailSlurp has done serious work here: a hosted MCP endpoint, sixteen tools, five least-privilege roles from read-only to inbox manager, and an agent REST API. It is designed for an agent acting inside an organisation’s account, with OAuth and permissions around it. GrabMail’s server at https://grabmail.io/mcp is designed for the opposite case — an agent that has no account anywhere and needs an inbox now — so it asks for nothing and offers six tools, including a wait_for_message that blocks for up to 25 seconds.

If the agent is yours and the mail is your company’s, MailSlurp’s roles are the safer model. If the agent is signing itself up to a third-party service and the mail is a verification code, GrabMail’s keyless server removes the one step an unattended agent cannot do alone: getting through a sign-up. Email for AI agents covers the loop.

Switching from MailSlurp

A test suite that uses MailSlurp for inbound mail only moves in an afternoon; one that uses sending or webhooks should stay. The steps:

1. Replace inbox creation with an address. Where the suite called createInbox() and stored an id, build an address instead: run-${id}@grabmail.io, or any name on a domain you point here. Nothing has to be created.
2. Replace the wait with a loop. waitForLatestEmail becomes a GET on /api/v1/mailbox every second until count is above zero or the deadline passes. The guides have the function in TypeScript and Python; copy it once.
3. Remove the secret. Delete the MAILSLURP_API_KEY variable from CI and the SDK from the lockfile. If your pipeline pins outbound hosts, allow grabmail.io.
4. Check what you relied on. Attachments still work here (5 MB per message). Sending, SMS, IMAP and webhooks do not exist here, and mail is gone after 5 days.

Which one, for what

The honest split is by requirement:

When to stay with MailSlurp

Three situations where switching would cost you something real:

• Your tests carry real data. A GrabMail mailbox is readable by anyone who knows the address, on the public domains and on yours. MailSlurp inboxes belong to an account and can be scoped per agent. A test that mails a customer’s details needs the second.
• You depend on push or on sending. Webhooks, IMAP, SMTP, outbound mail and phone numbers are absent here by design and will stay absent. If any of them is in your suite, there is nothing to switch to.
• You have already paid for the year. MailSlurp’s fees are non-refundable. Run the two in parallel on the next project rather than tearing out a working one.

Questions