Overview

Stalwart Mail Server is an all-in-one mail and collaboration server written in Rust. A single binary is fluent in every major protocol — SMTP, IMAP, JMAP, POP3, CalDAV, CardDAV and WebDAV — making it a complete replacement for a traditional mail stack with a strong emphasis on security, speed and scalability.

Key Features

• All Protocols in One: SMTP, IMAP, JMAP, POP3, CalDAV, CardDAV and WebDAV in a single server
• JMAP Support: modern protocol with fast synchronisation and push notifications
• Built-in Security: MTA-STS, DANE, and automatic TLS/ACME
• Flexible Storage: SQLite, PostgreSQL or MySQL backends
• Built-in Filtering: spam and malware filtering with Sieve rules
• High Performance: memory-safe Rust with low resource usage

Why Use It

Stalwart collapses an entire mail server stack into one memory-safe binary. For self-hosters it offers a modern, protocol-rich alternative to older component-based stacks, with JMAP and push support out of the box and a genuinely readable configuration file.

Use Cases

• Running a modern, scalable mail server for a home lab, organisation or community
• Replacing a mailcow/Postfix+Dovecot stack with a single format-fluent daemon
• Deploying a mail server with CalDAV/CardDAV collaboration built in

Platforms

Linux (also runs on macOS and FreeBSD; deployed from binary or Docker images).

Licence

Open Source — AGPL-3.0.

Website

https://stalw.art/

Alternatives

• Mailcow — dockerised all-in-one mail server suite