Launching today
MailCue
Run as a fully hardened production email server.
55 followers
Run as a fully hardened production email server.
55 followers
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. Perfect for local development, CI/CD pipelines, and ensuring your transactional emails actually deliver.
Owl Browser
Hey Product Hunt! 👋
Building and scaling software products like Owl Browser taught our team a frustrating lesson: testing transactional email workflows is a massive headache. Simple SMTP catchers just don't cut it when you need to verify things like DKIM signing, DMARC alignment, spam filtering, or automated IMAP parsing. We were constantly forced to test in environments that looked nothing like production, leading to unexpected delivery issues down the line.
So, we built MailCue.
MailCue is a realistic, all-in-one email testing server packaged into a single Docker container. We combined Postfix, Dovecot, OpenDKIM, OpenDMARC, and SpamAssassin, and wrapped them in a modern React UI and a FastAPI REST backend.
Here is 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 entirely and inject emails directly via 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 databases, Redis, or queues required. Everything runs in one 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 completely open-source (MIT), and we designed it to be a shared development dependency you can easily plug into your Docker networks.
We would love for you to spin it up, 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 the architecture, setup, or our roadmap! 🚀