Postal

Postal provides a self‑hosted mail delivery platform that handles both incoming and outgoing email for websites and web servers. It offers a web‑based interface for managing servers, viewing logs, and configuring settings, allowing administrators to operate the service on their own infrastructure without relying on external providers. The system supports horizontal scaling, enabling users to adjust capacity as demand changes.

The platform includes webhook support to notify HTTP endpoints about delivery status or issues, and a development mode that can hold messages for testing purposes. It also manages IP pools, letting mail be sent from multiple addresses to maintain reputation. Integration with SpamAssassin, rspamd, and ClamAV provides spam filtering and antivirus scanning for both inbound and outbound traffic.

Postal is released under the MIT license, is open source, and does not require subscriptions or tiered pricing. It is positioned as a free, fully featured alternative to commercial email services such as Sendgrid, Mailgun, or Postmark, targeting developers and operators who need a controllable, extensible mail server.