Postal

Postal is a self-hosted mail delivery platform built as an alternative to commercial transactional email services like Sendgrid and Mailgun. If your application sends emails and you want to run that infrastructure yourself, Postal provides the full stack: SMTP server, sending queues, bounce handling, webhook tracking, and a management interface.

The feature set mirrors what you expect from a commercial sending platform. Incoming and outgoing mail processing, detailed delivery analytics, per-message tracking, IP pool management for reputation segmentation, and click and open tracking are all included. A web interface covers organization management, sending domains, DKIM configuration, and message logs.

Multiple sending servers can be grouped under a single Postal installation, making it suitable for agencies or SaaS platforms handling mail for multiple clients. Webhook delivery for bounce and delivery events makes it practical to build feedback loops into your application logic.

Postal is MIT-licensed with 16,000+ GitHub stars. The installation uses Docker Compose and the application is built on Ruby on Rails. Documentation lives at docs.postalserver.io and covers production deployment in detail.

The honest caveat is the same one that applies to all self-hosted transactional email: IP reputation and deliverability require active management. Commercial providers handle this work for you. With Postal you own the infrastructure and the reputation, which means both the cost savings and the accountability for maintaining good sending practices.