stalwartlabs/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.

Key features:

• Email server with complete protocol support:
  • JMAP:
    • JMAP for Mail server.
    • JMAP for Sieve Scripts.
    • WebSocket, Blob Management and Quotas extensions.
  • IMAP:
    • IMAP4rev2 and IMAP4rev1 server.
    • ManageSieve server.
    • Numerous extensions supported.
  • POP3:
    • POP3 server.
    • STLS and SASL support as well as other extensions.
  • SMTP:
    • SMTP server with built-in DMARC, DKIMv2, DKIMv1, SPF and ARC support for message authentication.
    • Strong transport security through DANE, MTA-STS and SMTP TLS reporting.
    • Automated DKIM key rotation and management.
    • Inbound throttling and filtering with granular configuration rules, sieve scripting, MTA hooks and milter integration.
    • Distributed virtual queues with delayed delivery, priority delivery, quotas, routing rules and throttling support.
    • Envelope rewriting and message modification.
• Collaboration server:
  • Calendaring and scheduling:
    • CalDAV and CalDAV Scheduling support.
    • JMAP for Calendars support.
  • Contact management:
    • CardDAV support.
    • JMAP for Contacts support.
  • File storage:
    • WebDAV support.
    • JMAP for File Storage support.
  • Sharing with fine-grained access controls:
    • WebDAV ACL support.
    • JMAP Sharing support.
• Spam and Phishing built-in filter:
  • Comprehensive set of filtering rules on par with popular solutions.
  • LLM-driven spam filtering and message analysis.
  • Statistical spam classifier with collaborative filtering, automatic training capabilities and address book integration.
  • DNS Blocklists (DNSBLs) checking of IP addresses, domains, and hashes.
  • Collaborative digest-based spam filtering with