Secure & Modern All-in-One Mail Server (IMAP, JMAP, POP3, SMTP) 🛡️

Features

Stalwart Mail Server is an open-source mail server solution with JMAP, IMAP4, POP3, and SMTP support and a wide range of modern features. It is written in Rust and designed to be secure, fast, robust and scalable.

Key features:

• JMAP server:
  • JMAP Core and JMAP Mail full compliance.
  • JMAP for Sieve Scripts extension for managing Sieve scripts.
  • JMAP for WebSocket, JMAP Blob Management and JMAP for Quotas extensions.
• IMAP4, POP3 and ManageSieve server:
  • IMAP4rev2 and IMAP4rev1 server with support for numerous extensions.
  • POP3 server with extensions, STLS and SASL support.
  • ManageSieve server for managing Sieve scripts.
• SMTP server:
  • Built-in DMARC, DKIM, SPF and ARC support for message authentication.
  • Strong transport security through DANE, MTA-STS and SMTP TLS reporting.
  • 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.
• Spam Phishing filter:
  • Comprehensive set of filtering rules on par with popular solutions.
  • Statistical spam classifier with automatic training capabilities.
  • DNS Blocklists (DNSBLs) checking of IP addresses, domains, and hashes.
  • Collaborative digest-based spam filtering with Pyzor.
  • Phishing protection against homographic URL attacks, sender spoofing and other techniques.
  • Trusted reply tracking to recognize and prioritize genuine e-mail replies.
  • Sender reputation monitoring by IP address, ASN, domain and email address.
  • Greylisting to temporarily defer unknown senders.
  • Spam traps to set up decoy email addresses that catch and analyze spam.
• Flexible and scalable:
  • Pluggable storage backends with RocksDB, FoundationDB, PostgreSQL, mySQL, SQLite, S3-Compatible, Redis and ElasticSearch support.
  • Clustering support with node autodiscovery and partition-tolerant failure detection.
  • Built-in, LDAP or SQL authentication backend support.
  • Full-text search available in 17 languages.
  • Sieve scripting language with support for all registered extensions.
  • Email aliases, mailing lists, subaddressing and catch-all addresses support.
  • Automatic account configuration and discovery with autoconfig and autodiscover.
  • Metrics, tracing, logging and alerts with OpenTelemetry and Prometheus integration.
  • Webhooks for event-driven automation.
  • Disk quotas.
• Web-based administration:
  • Account, domain, group and mailing list management.
  • SMTP queue management for messages and outbound DMARC and TLS reports.
  • Report visualization interface for received DMARC, TLS-RPT and Failure (ARF) reports.
  • Configuration of every aspect of the mail server.
  • Log viewer with search and filtering capabilities.
  • Self-service portal for password reset and encryption-at-rest key management.
• Secure and robust:
  • Encryption at rest with S/MIME or OpenPGP.
  • Automatic TLS certificate provisioning with ACME using TLS-ALPN-01, DNS-01 or HTTP-01 challenges.
  • OAuth 2.0 authorization code and device authorization flows.
  • Two-factor authentication with Time-based One-Time Passwords (2FA-TOTP)
  • Application passwords (App Passwords).
  • Automated blocking of hosts that cause multiple authentication errors (aka fail2ban).
  • Access Control Lists (ACLs).
  • Rate limiting.
  • Security audited (read the report).
  • Memory safe (thanks to Rust).