Over Stalwart
Stalwart is an open-source mail & collaboration server with JMAP, IMAP4, POP3, SMTP, CalDAV, CardDAV and WebDAV support and a wide range of modern features. It is written in Rust and designed to be secure, fast, robust and scalable.

Features
All-in-One Platform
- Comprehensive email and collaboration tools in a single binary
 - Built in Rust for memory safety and performance
 - Unified configuration across all components
 - JMAP, IMAP, SMTP, CalDAV, CardDAV, and WebDAV support
 
Enhanced Security
- Encryption at rest with S/MIME and OpenPGP
 - Strong transport security via DANE, MTA-STS, and TLS Reporting
 - Automatic TLS certificate provisioning with ACME
 - Granular access controls, rate limiting, and fail2ban protection
 - Security-audited codebase
 
Advanced Spam & Phishing Protection
- Built-in DMARC, DKIM, SPF, and ARC authentication
 - Statistical spam classifier with automatic training
 - DNS Blocklists for IPs, domains, and content hashes
 - Phishing protection against homographic and spoofing attacks
 - Sender reputation monitoring and greylisting
 
Highly Flexible
- Enhanced Sieve scripting capabilities
 - Dynamic configuration rules
 - Full-text search across 17 languages
 - Multiple storage and authentication backend options
 - Web-based interface with self-service portal
 
Built to Scale
- Seamless load balancing and fault tolerance
 - Node autodiscovery for easy network expansion
 - Partition-tolerant failure detection
 - Simplified architecture without coordinators or proxies
 
Unified Collaboration
- Calendar and event scheduling with free/busy support
 - Rich contact management
 - File storage and secure sharing
 - Real-time syncing across devices