Stalwart

Host email, calendars, contacts, and shared files on one server.

Stalwart is a self-hosted mail and collaboration server written in Rust. It supports email through JMAP, IMAP, POP3, and SMTP, alongside CalDAV calendars, CardDAV contacts, and WebDAV file access.

It includes web-based administration, spam filtering, and configurable storage backends. Community and commercial licensing options are available; features and support vary by edition.