At a glance
Fourteen rows, and several are “not comparable” by nature: a sandbox that captures outbound mail has no public domains and no inbox anyone can write to. Every Mailtrap cell is what its pricing page, Sandbox page, Agent Inbox page and documentation said on 2 September 2026; every GrabMail cell is read from the constants the service enforces.
| Feature | GrabMail | Mailtrap |
|---|---|---|
| Free tier | Yes: Everything: public domains, your own domain, the API and the MCP server. No account, no card. | Partly: Sandbox: 50 test emails a month, 1 sandbox, 10 emails kept per sandbox, no address to mail into. Sending: 4,000 emails a month. |
| No account, no API key | Yes: Nothing to create. A GET with the address in the query string reads the mailbox. | No: An account, and an API token on every call. |
| REST API | Yes: Three endpoints over HTTPS, OpenAPI 3.1, one read per second per address. | Yes: Sandbox and Sending APIs on every plan, with SDKs and a CLI. |
| Choose your own address | Yes: Any name on 8 public domains, grabmail.io and mixozia.com among them, free. | Partly: Sandbox addresses are assigned on paid plans; Agent Inbox gives a hosted address, or your own domain. |
| Your own domain | Yes: Free and unlimited: one MX record at smtp.grabmail.io, no registration step. | Partly: For sending: 1 domain free, 5 on Basic, 100 on Business. For receiving: Agent Inbox with a custom domain. |
| Message retention | 5 days, fixed. Not a tier, not a setting. | Sandbox: a count, not a time — 10 emails per sandbox free, 50 on Basic, 200 on Team, 600 on Business, oldest out first. |
| Attachments | Yes: Up to 5 MB per message, downloadable from the inbox and the API. | Yes: Yes, in captured messages; size limit not published. |
| No ads, no tracking | Yes: No ads, no analytics, no third-party script. | Yes: No advertising; a paid SaaS. |
| Private inbox | No: Public: anyone who knows the address can read it. Each mailbox has an alias to hand out instead. | Yes: Private: sandboxes live inside an account and can be shared with named users. |
| MCP server for AI agents | Yes: Free MCP server at https://grabmail.io/mcp: create an inbox, wait up to 25 seconds for a message, read it. | Yes: An official MCP server (npx -y mcp-mailtrap), an llms.txt, a CLI, and Agent Inbox for agents that receive mail. Needs an account token. |
| Sending mail | No: None, by design. Receive only. | Yes: Yes: a full sending product, 4,000 emails a month free, with webhooks for opens, clicks and bounces. |
| Webhooks or push | No: None. Poll once a second, or let the MCP wait hold the call open. | Yes: Webhooks on sending events; forwarding rules from a sandbox to allowed recipients on paid plans. |
| Official SDKs | No: None. An OpenAPI document and three endpoints instead. | Yes: Python, PHP, Ruby, Node.js and Java, plus a CLI. |
| Apps and extensions | Partly: A Chrome extension, loaded by hand; not on the store yet. | Partly: No app or extension; a CLI and integrations with Supabase, Vercel, Claude and Cursor. |
Checked 2 September 2026. Mailtrap sells three products — Email Sandbox, Email API/SMTP for sending, and Agent Inbox — and the table names which one a cell refers to. Sandbox retention is a count per sandbox, not a time; the note in that row says so.
What Mailtrap does well
Mailtrap is the standard answer to “how do I stop staging from emailing customers”, and it has grown well past that. Four things it does that GrabMail does not:
- It catches what you send. Point your application’s SMTP at the Sandbox and every message it sends lands in a sandbox instead of a person’s inbox, with HTML compatibility checks, a spam score and previews across real clients. GrabMail sees only what the outside world sends to it.
- It sends for real. The Email API/SMTP product delivers transactional mail from your domain, 4,000 a month free, with event webhooks. GrabMail cannot send a single message.
- It has an agent story on both sides. An official MCP server, an
llms.txt, a CLI, and Agent Inbox, where an agent receives real mail at a hosted address or your domain and can reply — twenty times on the hosted one, without limit on your own. - Teams and forwarding. Sandboxes shared with named users, forwarding to whitelisted recipients on paid plans, SSO on Enterprise. GrabMail has no users, because it has no accounts.
Where GrabMail is different
GrabMail answers the question the Sandbox does not: a test has signed up to somebody else’s service, and now it needs to read what that service sent.
- Real addresses that receive from anyone. Mail from Google, from Stripe, from the app you are testing against — delivered to
run-42@grabmail.ioor to any address on a domain you point at smtp.grabmail.io. Mailtrap’s Sandbox has no MX record and bounces such mail; only its paid sandbox address and Agent Inbox receive from outside. - No account, no token, no cap. Mailtrap’s Free plan is 50 test emails a month and 10 kept per sandbox, behind an account and a token. GrabMail keeps every message 5 days, on any number of addresses, with a keyless GET and one read a second per address as the only limit.
- Your own domain, free, for receiving. One MX record makes a domain a catch-all inbox, unlimited. Mailtrap’s domains are for sending, and Agent Inbox’s custom domain is part of a paid product.
- An MCP server with no login. Mailtrap’s MCP server needs an account token; GrabMail’s at https://grabmail.io/mcp needs nothing and gives an agent
create_inboxand a blockingwait_for_messageof up to 25 seconds — the two calls an agent signing itself up somewhere needs.
Price, side by side
Mailtrap’s Email Sandbox is priced monthly in US dollars, about twenty percent less on annual billing; the sending product is priced separately by volume. 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.
| Tier | GrabMail | Mailtrap Email Sandbox |
|---|---|---|
| Free | Public domains, your own domain, API, MCP. No account, no cap. | 50 test emails a month, 1 user, 1 sandbox, 10 emails per sandbox, no sandbox email address. |
| Cheapest paid | Premium, $24 a month: API access to the off-blocklist domain pool, paid in crypto. | Basic, $17 a month or $14 billed annually: 500 test emails, 3 users, 50 per sandbox, 100 forwarded emails, a sandbox address to mail into. |
| Team tier | Pro $78 and Scale $148 a month: more messages and keys on the same pool. | Team, $42 or $34 annually: 5,000 test emails, 5 sandboxes, 200 per sandbox. Business, $123 or $99 annually: 50,000, 50 sandboxes, 600 per sandbox. |
| Enterprise | None. There is no contract tier and no SLA. | $498 a month or $399 annually: unlimited test emails and users, 300 sandboxes, SSO. Sending is priced apart, from $0 for 4,000 a month. |
Prices as published on 2 September 2026. GrabMail’s pricing page has the full grid.
For developers: reading a mailbox
The two APIs do different jobs, so here is the one that reads inbound mail. 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 Mailtrap Sandbox API lists messages a sandbox has captured from your own application, with an account token — the right call for asserting that your app sent the right thing. Reading a message the outside world sent to a test user is GrabMail’s job: the reference is three endpoints, and the Playwright and GitHub Actions guides show a suite that signs up and waits for the code.
The two compose rather than compete. A full end-to-end test of your own sign-up flow can point the application’s SMTP at Mailtrap to check the template, and point a real third-party sign-up at a GrabMail address to check that the code arrives and works. The API comparison lists the other services on the inbound side.
For AI agents
Mailtrap has invested here: an official MCP server, an llms.txt, a CLI, and Agent Inbox, a product built for agents that receive and reply to real mail from a hosted address or your domain. All of it sits inside an account with a token. GrabMail’s server at https://grabmail.io/mcp sits outside any account: create_inbox, a blocking wait_for_message of up to 25 seconds, read_message, no login.
If the agent is yours and needs to reply, Mailtrap’s Agent Inbox is the more complete product. If the agent is signing itself up to a third-party service and needs a code, GrabMail’s keyless server removes the step it cannot do alone. Email for AI agents covers the loop.
Switching from Mailtrap
Usually you should not switch; you should add. Where a switch is really a switch:
- Identify the tests that receive. Any test that signs up to something outside your codebase and waits for its mail belongs on an inbound service. Give it
run-{id}@grabmail.io, or an address on a domain you point atsmtp.grabmail.io. - Leave the tests that send where they are. Template checks, spam scores and previews of your own outbound mail are the Sandbox’s job, and GrabMail cannot do them.
- Drop the token for the inbound half. The GrabMail calls carry no header, so the receiving tests can run on a fork’s pipeline with no secret configured.
- Keep Agent Inbox if the agent replies. GrabMail cannot send; an agent that has to answer mail needs Mailtrap’s product or something like it.
Which one, for what
The honest split is by direction:
Pick GrabMail when
- a test or an agent must receive mail from a third party and read a code or a link;
- you want unlimited real addresses, on public domains or your own, with no account;
- the call must be keyless and free.
Pick Mailtrap when
- you need to inspect what your own application sends, before it reaches anyone;
- you send transactional mail and want events, logs and previews in one place;
- an agent has to reply to mail, or a team needs shared sandboxes and SSO.
When to stay with Mailtrap
Three situations where switching would be a mistake:
- Your tests check outbound mail. GrabMail cannot see what your app sends. That is the Sandbox’s entire purpose, and nothing here replaces it.
- You send. GrabMail has no sending path and will not add one; Mailtrap’s Email API is a real product with a free tier.
- Your mail is private. A sandbox is inside your account; a GrabMail mailbox is readable by anyone who knows the address, on the public domains and on yours.
Questions
Is GrabMail an alternative to Mailtrap?
Only for one of Mailtrap’s three products, and only in the other direction: GrabMail receives real inbound mail at real addresses, which the Email Sandbox does not do and Agent Inbox does inside a paid account. For capturing and inspecting your own outbound mail, or for sending, there is no GrabMail equivalent.
Can Mailtrap receive email from the outside world?
The Sandbox cannot: its documentation says it provides no MX records to catch inbound email, so such mail bounces. Paid Sandbox plans include an address you can mail into from another account, and Agent Inbox receives real mail at a hosted address or your own domain.
What does the free Mailtrap Sandbox include?
50 test emails a month, one user, one sandbox holding 10 emails at a time with the oldest dropped first, and no sandbox address. Sending has a separate free tier of 4,000 emails a month. GrabMail’s free tier has no monthly count.
Which one has an MCP server?
Both. Mailtrap’s is official, installed with npx -y mcp-mailtrap, and needs an account token; GrabMail’s is hosted at https://grabmail.io/mcp, needs nothing, and includes a blocking wait_for_message. The client guide has GrabMail’s configuration.
Can I use both in one test suite?
That is the usual arrangement: point the application under test at the Sandbox to check what it sends, and give third-party sign-ups a GrabMail address to check what arrives. The two never compete for the same message.
