A free Mailsac alternative — no API key needed to start

Mailsac's public inboxes need no signup either, but reading them over the API does. receivemail.dev skips the API key entirely — one POST, no account.

Mailsac is a mature email-testing API: any @mailsac.com address receives mail with no signup, and a free account adds an API key, 1 private address, and 1,500 operations a month — paid plans scale from there (25,000 ops/mo and up). It's a solid choice if you want a long-lived account with usage history and room to grow.

If the job is narrower — in an automated test, sign up for something and read the verification email back — receivemail.dev skips the account step entirely. There's no API key to generate or store, even for private, non-public inboxes: one unauthenticated POST creates the mailbox and returns a secret that gates reading it.

Side by side

	receivemail.dev	Mailsac
Price	Free	Free tier (1,500 ops/mo), then from $18/mo
Signup / account	None	Not required for public inboxes; required for API key / private inboxes
API key	No	Yes, for API access
Private inbox without signup	Yes — every inbox is private by default	No — no-signup inboxes are public
Operations/month limit	None published (rate-limited per IP instead)	1,500 free, then plan-based
Own domain support	No	Yes (paid)
Retention	Up to 60 min TTL	Longer, plan-dependent

Mailsac's plans and operation limits change over time — see mailsac.com/pricing for current numbers.

When receivemail.dev is enough

• You want a private inbox without ever creating an account or key.
• The test only needs to read one code/link, not manage ongoing volume.
• You want contributors to run the suite with zero setup.

When to choose Mailsac instead

• You're sending real volume and want a tracked monthly operations budget.
• You want your own domain receiving test mail.
• You want an account with history/dashboard across a team.

Migrating a test

# Mailsac: GET /api/addresses/:email/messages with X-Mailsac-Key
resp=$(curl -s -X POST https://receivemail.dev/mailboxes)
addr=$(echo "$resp" | jq -r .address)
secret=$(echo "$resp" | jq -r .secret)

# ... run your signup against $addr ...

curl -s "https://receivemail.dev/mailboxes/$addr/messages" \
  -H "Authorization: Bearer $secret"

Full walkthrough: the CI testing guide.

Other alternatives people compare

• MailSlurp — full email platform, send + receive. See the MailSlurp comparison.
• Mailinator — free public inboxes, paid private domains. See the Mailinator comparison.
• Mailosaur — paid email + SMS testing for QA teams. See the Mailosaur comparison.