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, IMAP4, POP3 and ManageSieve server:
  • JMAP server with Sieve Scripts, WebSocket, Blob Management and Quotas extensions.
  • 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.
• Built-in Spam and Phishing filter:
  • Comprehensive set of filtering rules on par with popular solutions.
  • LLM-driven spam filtering and message analysis.
  • 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.
  • 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.
  • Multi-tenancy support with domain and tenant isolation.
  • Disk quotas per user and tenant.
• 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.
  • Automated blocking of IP addresses that attack, abuse or scan the server for exploits.
  • Rate limiting.
  • Security audited (read the report).
  • Memory safe (thanks to Rust).
• Authentication and Authorization:
  • OpenID Connect authentication.
  • OAuth 2.0 authorization with authorization code and device authorization flows.
  • LDAP, OIDC, SQL or built-in authentication backend support.
  • Two-factor authentication with Time-based One-Time Passwords (2FA-TOTP)
  • Application passwords (App Passwords).
  • Roles and permissions.
  • Access Control Lists (ACLs).
• Observability:
  • Logging and tracing with OpenTelemetry, journald, log files and console support.
  • Metrics with OpenTelemetry and Prometheus integration.
  • Webhooks for event-driven automation.
  • Alerts with email and webhook notifications.
  • Live tracing and metrics.
• Web-based administration:
  • Dashboard with real-time statistics and monitoring.
  • 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.

Install Stalwart Mail Server on your server by following the instructions for your platform:

• Linux / MacOS
• Windows
• Docker

All documentation is available at stalw.art/docs/get-started.

If you are having problems running Stalwart Mail Server, you found a bug or just have a question, do not hesitate to reach us on GitHub Discussions, Reddit, Discord or Matrix. Additionally you may purchase an premium support to obtain priority support from Stalwart Labs LLC.

Your support is crucial in helping us continue to improve the project, add new features, and maintain the highest level of quality. By becoming a sponsor on Open Collective, you help fund the development and future of Stalwart Mail Server. As a thank-you, sponsors who contribute $10 per month or more will automatically receive a Small Business Edition license, which includes all the powerful features of the Enterprise edition.

These are some of our open-source sponsors:

If you would like to support our work, please consider becoming a sponsor.

• CalDAV, CardDAV and WebDAV support
• JMAP Calendar, Contacts and Tasks support
• ActiveSync support

See the enhancement requests page for a full list of proposed features by the community.

Part of the development of this project was funded through the NGI0 Entrust Fund, a fund established by NLnet with financial support from the European Commission's Next Generation Internet programme, under the aegis of DG Communications Networks, Content and Technology under grant agreement No 101069863.

If you find the project useful you can help by becoming a sponsor. Thank you!

This project is dual-licensed under the GNU Affero General Public License v3.0 (AGPL-3.0; as published by the Free Software Foundation) and the Stalwart Enterprise License v1 (SELv1):

• The GNU Affero General Public License v3.0 is a free software license that ensures your freedom to use, modify, and distribute the software, with the condition that any modified versions of the software must also be distributed under the same license.
• The Stalwart Enterprise License v1 (SELv1) is a proprietary license designed for commercial use. It offers additional features and greater flexibility for businesses that do not wish to comply with the AGPL-3.0 license requirements.

Each file in this project contains a license notice at the top, indicating the applicable license(s). The license notice follows the REUSE guidelines to ensure clarity and consistency. The full text of each license is available in the LICENSES directory.

Copyright (C) 2024, Stalwart Labs Ltd.