Mailsac alternative: GrabMail vs Mailsac

At a glance

Fourteen rows. Every Mailsac cell is what its pricing page, FAQ and documentation 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. Mailsac renders monthly prices in its page and yearly ones only in its pricing script ($169 Indie, $840 Business); both are quoted. It publishes no requests-per-second figure, only the monthly operations quota and a right to throttle anyone, paid or not.

What Mailsac does well

Mailsac has run since 2011 and sits between the public services and the big platforms on both price and scope. Four things it does that GrabMail does not:

• Push, four ways. A message arriving at a private address or a custom domain can be posted to a webhook, pushed over a websocket, forwarded to Slack, or pulled by POP3. A workflow that cannot poll has options here; GrabMail offers only polling and the MCP wait.
• Private addresses at a low price. One private address on the free plan, fifty on Indie at $18 a month. Mail to them is visible only to the account. Every GrabMail mailbox is public, at every price.
• Retention you can grow. Private mail is kept until your storage quota recycles it, and a starred message is never recycled. GrabMail deletes after 5 days, whatever you do.
• Tools around the inbox. Load testing, an outbound capture service, delete-everything-on-a-domain, IP allowlists, SSO on Business, and a public forum with the team in it. GrabMail is three endpoints and a status page.

Where GrabMail is different

GrabMail keeps the part of Mailsac that people love — make up an address, receive at once — and removes the meter and the key.

• No key, no quota. Mailsac counts every API call as an operation and stops at 1,500 a month on the free plan; a suite polling one inbox every second uses that in twenty-five minutes. GrabMail’s API has no key, no account and no monthly count — one read a second per address, all month.
• A more useful public inbox. On Mailsac a public inbox holds six messages for four days, capped at 2.5MB, with attachments reachable only through the API. Here a mailbox holds every message for 5 days, each up to 5 MB, attachments downloadable from the page and the API.
• Your own domain, free. Mailsac’s custom domain is $7 a month or a subdomain of its own msdc.co. Here any domain you point at smtp.grabmail.io is a catch-all inbox for nothing — and, unlike Mailsac’s, it does not buy privacy, which the row above says plainly.
• An MCP server for agents. Mailsac has none. GrabMail’s at https://grabmail.io/mcp gives an agent an inbox and a blocking wait_for_message of up to 25 seconds, with no key.

Price, side by side

Mailsac’s prices are in US dollars, monthly or yearly, with add-ons per domain, per block of operations and per block of storage; all sales are final. 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. Mailsac’s terms: no refunds, no SLA for any customer, and a right to throttle. GrabMail’s plans are prepaid from a crypto balance and carry no SLA either. 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 Mailsac equivalent is GET https://mailsac.com/api/addresses/name@mailsac.com/messages with a Mailsac-Key header — the same shape, one header more, and one operation off the month’s quota. The two APIs are close enough that a wait loop written for one is a base URL change for the other; the Python and Node.js guides have the GrabMail version.

The quota is the thing to design around if you stay on Mailsac: a loop that polls every second burns 3,600 operations an hour, so its documentation steers you to webhooks or websockets. On GrabMail polling once a second is the intended pattern, and the only ceiling is per address.

For AI agents

Mailsac publishes no MCP server and no llms.txt; an agent can call its REST API with the account’s key like any script, and every call costs an operation. 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.

For an agent that must sign itself up somewhere, the keyless server is the difference between finishing and stopping at a form. Email for AI agents covers the four-call loop and the guard rails for an agent nobody is watching.

Switching from Mailsac

The two are near twins on the inbound path, so the switch is short:

1. Change the base URL. mailsac.com/api/addresses/{address}/messages becomes grabmail.io/api/v1/mailbox?address={address}; a message is read at /api/v1/message/{id}?mailbox={address}. Field names are close; the ids are not, so do not persist them across services.
2. Drop the header and the quota logic. Remove Mailsac-Key from the request and the environment, and any back-off you wrote around the monthly operations count. Keep a one-second interval per address.
3. Point your domain here, if you had one. Change its MX record from Mailsac’s to smtp.grabmail.io, priority 10. It becomes a catch-all inbox here for free — and public, where Mailsac’s was private.
4. Replace push with polling or a wait. Webhooks, websockets, Slack and POP3 have no equivalent here. A test suite polls; an agent uses the MCP wait. If neither fits, stay.

Which one, for what

The honest split:

When to stay with Mailsac

Three situations where switching would cost you something real:

• Your tests carry real data. Mailsac’s private addresses and custom domains keep mail inside the account. Every GrabMail mailbox is public, on the public domains and on yours. A test that mails a customer’s details needs the first.
• You depend on push. A workflow built on Mailsac webhooks or websockets has nothing to move to here: GrabMail is poll-only by design.
• You keep mail for weeks. Starred messages and private storage on Mailsac last as long as your quota; GrabMail’s 5 days are a hard limit. An audit trail of test mail should stay where it is kept.

Questions