Postal

Postal is an open source mail server platform built for developers and organizations that need reliable outbound and inbound email handling. Originally created by Adam Cooke and now maintained by a community of contributors, Postal runs on Linux and provides a web-based control panel for managing domains, mail queues, and real-time logs. It supports SPF, DKIM, and DMARC out of the box to improve deliverability. For incoming mail, Postal can parse messages and send them to your application via HTTP webhooks. This makes it a good fit for apps that need to process replies, bounce notifications, or other automated email flows. The platform uses a queuing system with per-domain rate limiting and IP pools to spread sending across multiple addresses. It also includes a simple REST API for sending and managing mail programmatically. Postal stores all messages and can retain them for a configurable period, which helps with debugging and compliance. Setup requires a dedicated server with Docker and of course a mail stack. It is not a hosted service you sign up for; you deploy it on your own infrastructure. The project is written in Ruby and uses MySQL or MariaDB as its database backend. Postal is a solid choice for anyone who wants to self-host their outbound mail infrastructure without resorting to simplistic SMTP relays, and it is especially popular among SaaS developers.