Stalwart Mail Server is an all-in-one, secure, and scalable mail and collaboration server designed for modern email infrastructure. It supports multiple protocols including IMAP, JMAP, SMTP, and CalDAV/CardDAV, targeting system administrators and organizations seeking a robust, self-hosted email solution.

How It Works

Written in Rust, Stalwart leverages Rust's memory safety and performance benefits. It offers a comprehensive suite of features including built-in DMARC, DKIM, SPF, ARC, DANE, MTA-STS, and LLM-driven spam filtering. Its architecture is designed for fault tolerance and scalability, featuring a coordinator-free design, Kubernetes support, and pluggable storage backends for flexibility.

Quick Start & Requirements

• Install: Instructions available for Linux/macOS, Windows, and Docker.
• Documentation: stalw.art/docs/get-started
• Prerequisites: Rust toolchain recommended for building from source. Docker is a common deployment method.

Highlighted Details

• Full JMAP, IMAP4rev2, POP3, and ManageSieve server with extensive extension support.
• Advanced spam and phishing filtering, including LLM-driven analysis and collaborative digest-based filtering.
• Pluggable storage backends supporting RocksDB, PostgreSQL, MySQL, SQLite, S3-compatible, and more.
• OpenID Connect and OAuth 2.0 authentication, with support for LDAP, OIDC, SQL, and built-in backends.

Maintenance & Community

• Actively developed by Stalwart Labs.
• Community support via GitHub Discussions, Reddit, and Discord.
• Premium support available for purchase.
• Roadmap includes CalDAV, CardDAV, WebDAV, and JMAP Calendar/Contacts/Tasks support.

Licensing & Compatibility

• Dual-licensed under GNU Affero General Public License v3.0 (AGPL-3.0) and Stalwart Enterprise License v1 (SELv1).
• AGPL-3.0 requires derivative works to be open-sourced under the same license. SELv1 is a proprietary license for commercial use.

Limitations & Caveats

The AGPL-3.0 license may impose significant restrictions on commercial use or integration into closed-source products. ActiveSync support is listed as a future roadmap item.