Mailtrap Alternative for Email Testing

Mailtrap sells three products on separate plans: Email Sandbox catches test mail, Email API sends production mail, and Email Marketing sends campaigns. smtp.dev replaces only the sandbox. It never delivers to real recipients, so production email stays with whoever sends it today, Mailtrap included.

The two sandboxes meter different things. Mailtrap counts test emails per month and keeps a fixed number of messages per sandbox. smtp.dev counts domains and accounts, and keeps every message for a set number of days.

At a Glance

Stay on Mailtrap When

• Production mail goes through Mailtrap's Email API, and you want test mail in the same dashboard.
• You rely on the HTML check, the spam score, bounce emulation, or client previews. The audit here checks sender configuration, HTML structure, links, and images. It doesn't render the message in Gmail or Outlook.
• Several people need their own login, or you need SSO.
• Your tests use Mailtrap's SDKs and pass. Porting tests that already work adds cost and no coverage.

Reasons to Switch

• Receiving on the free plan. Mailtrap's Free sandbox has no inbound address. Lite receives on your domain as soon as its MX record resolves, so an OTP from your auth provider or a receipt from your payment provider lands in a real account.
• Your own domain. Test users can be jane@test.example.com and sam@test.example.com, each with its own inbox, instead of + tags on one sandbox address. example.com keeps its production MX.
• No monthly count. Basic's 500 test emails last 25 runs of a suite that sends 20. Plans here don't count messages.
• Retention by date. A Free sandbox keeps the newest 10 messages and Basic the newest 50, deleting older ones as new mail arrives. Here, last night's failed run is still there in the morning.
• IMAP. Every account is an IMAP and POP3 mailbox on every plan, so a test message opens in Thunderbird or Apple Mail.

Moving a Test Suite

Add a test domain such as test.example.com and point its MX record at mx.smtp.dev (how). Create an account for each address your tests use. Tests that relied on + tags keep them: qa+run42@test.example.com delivers to qa@test.example.com on every plan. On Pro and Max, a catch-all accepts any address.

Then change the app's SMTP settings:

send.smtp.dev delivers only to accounts in your sandbox and refuses any other recipient. Fixtures that mail user@example.com fail until they use addresses on your test domain.

If the app sends through a real provider to an inbox.mailtrap.io address, leave its SMTP settings alone and change the recipient instead.

Tests that fetch a message from a Mailtrap sandbox fetch it from the account's INBOX, newest first:

curl "https://api.smtp.dev/accounts/{accountId}/mailboxes/{mailboxId}/messages" \
  -H "X-API-KEY: $SMTP_DEV_API_KEY"

The API quickstart has a wait-and-assert helper, and the Playwright and Cypress guides use it in browser tests.