Hey Product Hunt! 👋
Building and scaling software products like Owl Browser taught our team a frustrating lesson: testing transactional email workflows is a headache. Simple SMTP catchers just don’t cut it when you need to verify things like DKIM signing, DMARC alignment, spam filtering, or automatic IMAP parsing. We were constantly forced to test in an environment that looked nothing like production, leading to unexpected delivery issues.
So, we made it Mel Q.
MailQ is a realistic, all-in-one email testing server packaged in a Docker container. We combined Postfix, Dovecot, OpenDKIM, OpenDMARC, and SpamAssassin, and wrapped them in a modern React UI and FastAPI REST backend.
Here’s what makes it special:
Realistic production behavior: It doesn’t just catch emails; It generates realistic headers, multi-hop received chains, simulated DKIM-signatures, and authentication results.
Full API control: Bypass SMTP completely and inject emails directly through our REST API. Perfect for deterministic testing in your CI/CD pipelines.
A complete mail stack: Read captured emails via standard IMAP/POP3 clients, or use the built-in responsive web interface.
Zero Infrastructure Mess: No external database, Redis, or queues required. Everything runs in a container managed by s6-overlay.
Production Ready Switch: Set MAILCUE_MODE=production to flip from a catch-all test sandbox to a fully hardened, live email server with strict virtual domains and TLS enforcement.
MailCue is fully open source (MIT), and we’ve designed it to be a common development dependency that you can easily deploy into your Docker networks.
We’d love for you to give it a spin, try breaking it, and let us know what you think. I’ll be hanging out in the comments all day to answer any questions about architecture, setup, or our roadmap! 🚀