Stalwart Mail Server

Stalwart Mail Server is an all-in-one mail and collaboration server built to provide a modern, standards-based alternative to assembling multiple separate components. It combines email delivery and storage, groupware protocols, and built-in security controls in a single, scalable service written in Rust.

Key Features

• Multi-protocol email support including SMTP, IMAP4, POP3, and JMAP
• Collaboration protocols including CalDAV, CardDAV, and WebDAV for calendars, contacts, and file storage
• Integrated spam and phishing defenses, including filtering rules, DNS blocklists, greylisting, and a statistical classifier
• Email authentication and transport security features such as DKIM, SPF, DMARC, ARC, MTA-STS, DANE, and TLS reporting
• Flexible backends for storage and search, with support for multiple databases and optional external search engines
• Built-in web-based administration with real-time stats, queue management, reporting views, and log exploration
• Authentication options including LDAP, SQL, and OpenID Connect, plus roles/permissions and ACLs
• Observability via logging/tracing and metrics integrations, with webhook-based event automation

Use Cases

• Replace a traditional MTA + IMAP store + spam filter stack with a single integrated platform
• Run a domain email service with modern clients via JMAP while retaining IMAP/POP3 compatibility
• Provide calendars, contacts, and file sharing for teams using CalDAV/CardDAV/WebDAV

Limitations and Considerations

• Some advanced scaling and backend options can add operational complexity compared to small single-node deployments

Stalwart Mail Server is well-suited for organizations and individuals who want a secure, standards-compliant email and collaboration platform with modern protocols, integrated protection against abuse, and deployment flexibility from small setups to large clustered environments.