Products/Testing and QA software/MailCue

MailCue

Run as a fully hardened production email server.

Testing and QA software2 peopleFounded 2026All-in-one Docker container with Postfix, Dovecot, SpamAssassinDKIM/DMARC verificationModern React UI with FastAPI REST backendIMAP/POP3 access for reading emailsREST API for direct email injection (bypass SMTP)Real-time eventsGPG encryption supportRealistic headers and multi-hop Received chainsSimulated DKIM-Signatures and Authentication-ResultsProduction mode switch (MAILCUE_MODE=production)Let's Encrypt certificate support via certbotZero infrastructure mess - no external databases, Redis, or queues requiredManaged by s6-overlayMIT open-source license

Visit MailCue →

Our Take

Most email testing tools are glorified inboxes that accept mail and show you the body - they can't test DKIM signing, DMARC alignment, or spam filtering because they don't run an actual mail stack. MailCue drops a full Postfix/Dovecot/SpamAssassin rig into a single Docker container so your CI pipeline tests emails exactly how Gmail and Outlook will actually receive them. The production mode switch is the move - flip MAILCUE_MODE=production and this thing hardens into a real mail server with TLS enforcement and Let's Encrypt certs, zero external dependencies required. It solves the classic dev pain where unit tests pass but production deliverability fails because nobody caught the broken SPF record in staging.

MailCue is an all-in-one email testing server packaged in a single Docker container. Unlike simple catch-all SMTPs, it provides a fully-featured mail stack with Postfix, Dovecot, SpamAssassin, DKIM/DMARC verification, and a modern React UI. Test your email workflows exactly as they behave in production with IMAP/POP3 access, API injection, real-time events, and GPG encryption.

Problem It Solves

Testing transactional email workflows is frustrating because simple SMTP catchers don't cut it when you need to verify DKIM signing, DMARC alignment, spam filtering, or automated IMAP parsing. Teams are constantly forced to test in environments that look nothing like production, leading to unexpected delivery issues.

Target Customer

Developers, QA teams, and software companies building email workflows who need realistic email testing

Use Cases

Local development testing, CI/CD pipeline integration, Testing transactional email workflows, Ensuring email deliverability, Email authentication testing (DKIM/DMARC)

Pricing Details

Open source (MIT license)

Free Tier

Yes - fully free and open source

Differentiator

Unlike simple SMTP catchers, MailCue provides a fully-featured production mail stack that mirrors real-world email infrastructure including realistic headers, multi-hop Received chains, simulated DKIM-Signatures, and Authentication-Results. It can flip from test sandbox to fully hardened production server with strict virtual domains and TLS enforcement.

Traction

User Count: 64 · Notable Metrics: 82 points upvotes, Day Rank #17

Key Facts

The people behind MailCue

Akram H. Sharkar

profile

Fakrul H. Sarker

profile

Links

Website Source: product-hunt

Want products like this in your inbox every morning?

Five products. Every morning. Written by someone who actually cares whether they're good or not. Free forever, unsubscribe whenever.