What is MailFixture?
MailFixture is a receive-only email testing service built specifically for CI environments. It gives you real test inboxes via a single API call, so your application can send actual emails—OTPs, magic links, verification codes—and your test suite receives them parsed, typed, and ready to assert. Instead of wrestling with fake mail servers or disposable inboxes that end up on blocklists, MailFixture hands your tests a genuine inbox that behaves like a real one, with delivery typically landing in under a second.
Who it's for
- CI/CD engineers who are tired of flaky email tests that pass locally but fail on the pipeline due to timing issues or shared test domains.
- QA automation teams using Playwright, Cypress, pytest, or Selenium who need deterministic OTP and link extraction without writing fragile regex parsers.
- AI agent developers who want their LLM-powered tools to autonomously create inboxes, trigger signup flows, and read verification codes back via MCP.
Key features
Long-polling built in
waitForMessage() holds the connection open until the email arrives—usually under a second after your app sends it. No sleep(5000), no polling loops every 500ms, no "flaky on CI, fine locally" excuses. The API waits for you, not the other way around.
First-class extraction
Every message arrives pre-parsed. The one-time code, magic link, and verification link are classified and sitting in an extracted field, alongside SPF/DKIM/DMARC verdicts and a SpamAssassin spam score. Your assertion is one line, and it doesn't break when marketing redesigns the email template.
Custom domains
Point one MX record at MailFixture and every fixture lives on tests.yourdomain.com. Because the domain is yours, it never gets flagged as "disposable email detected" by your own signup forms—a problem that plagues shared test-mail domains.
Dashboard and MCP support
The dashboard lets you watch inboxes fill in real time, with rendered HTML, plain text, headers, and raw source visible—plus the extracted OTP one click from your clipboard. MailFixture also works as a remote MCP server, so AI agents can create inboxes and read OTPs autonomously.
What stands out
"Delivered → parsed → asserted."
That's the entire promise in six words. Most email testing tools stop at delivery—they hand you a raw message and expect you to build the parsing and assertion logic yourself. MailFixture goes further by treating OTPs and verification links as first-class fields, not regex homework. Combined with long-polling that eliminates retry loops and custom domains that dodge blocklist issues, it removes the three biggest sources of email test flakiness in one shot.
Worth checking out if…
You're building end-to-end tests that depend on email delivery and you're tired of debugging why waitForTimeout(5000) isn't enough. If your team has ever shipped a broken signup flow because the OTP test passed locally but failed on CI, MailFixture's approach is worth a look. The free tier includes 100 messages per month with no credit card required, and paid plans start at $15/month with no per-seat pricing—you pay for messages, not people. It's also a strong fit if you're experimenting with AI agents that need to verify their own signup flows end to end.
