Mox

Mox provides a self‑hosted mail server that implements the full modern email stack, including SMTP and IMAP4 with extensions, webmail access, and automatic TLS via ACME/Let’s Encrypt. It handles authentication and integrity through SPF, DKIM, DMARC, DANE, MTA‑STS and DNSSEC, and offers both reputation‑based and Bayesian content filtering to keep junk out of users’ inboxes. Internationalized email addresses are supported, and account autoconfiguration simplifies client setup through SRV records and device‑management profiles.

The server is designed for low‑maintenance operation: a quick‑start command creates configuration files, generates passwords, and lists required DNS records, allowing a functional mail service to be up in minutes. Administration can be performed via a web interface or directly in the configuration file, and the built‑in web server can also serve static sites or act as a reverse proxy. An HTTP/JSON API, Prometheus metrics, and structured logging give developers and operators visibility into delivery events and system health.

Mox is written in Go, released under the MIT license, and includes extensive automated and fuzz testing as well as manual interoperability checks with major mail clients and providers. Its code references relevant RFCs for readability, and it can be run locally for testing with the “localserve” subcommand, making it suitable for both production deployments and development environments.