Stalwart is a mail and 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.
This is free and open source software.
Features include:
- 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, 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.
- JMAP:
- Collaboration server:
- Calendaring with CalDAV, CalDAV Scheduling and e-mail alarms support.
- Contact management with CardDAV support.
- File storage with WebDAV support.
- Sharing with WebDAV ACL support for fine-grained access control.
- 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 automatic training capabilities and address book integration.
- 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:
- Pluggable storage backends with RocksDB, FoundationDB, PostgreSQL, mySQL, SQLite, S3-Compatible, Azure, Redis and ElasticSearch 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.
- 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-01orHTTP-01challenges. - Automated blocking of IP addresses that attack, abuse or scan the server for exploits.
- Rate limiting.
- Security audited.
- Memory safe.
- Scalable and fault-tolerant:
- Designed to handle growth seamlessly, from small setups to large-scale deployments of thousands of nodes.
- Built with fault tolerance and high availability in mind, recovers from hardware or software failures with minimal operational impact.
- Peer-to-peer cluster coordination or with Kafka, Redpanda, NATS or Redis.
- Kubernetes, Apache Mesos and Docker Swarm support for automated scaling and container orchestration.
- Read replicas, sharded blob storage and in-memory data stores for high performance and low latency.
- 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.
Website: github.com/stalwartlabs/stalwart
Support:
Developer: Stalwart Labs LLC
License: GNU Affero General Public License v3.0
Stalwart is written in Rust. Learn Rust with our recommended free books and free tutorials.
| Popular series | |
|---|---|
 | The largest compilation of the best free and open source software in the universe. Each article is supplied with a legendary ratings chart helping you to make informed decisions. |
 | Hundreds of in-depth reviews offering our unbiased and expert opinion on software. We offer helpful and impartial information. |
 | The Big List of Active Linux Distros is a large compilation of actively developed Linux distributions. |
 | Replace proprietary software with open source alternatives: Google, Microsoft, Apple, Adobe, IBM, Autodesk, Oracle, Atlassian, Corel, Cisco, Intuit, SAS, Progress, Salesforce, and Citrix |
 | Awesome Free Linux Games Tools showcases a series of tools that making gaming on Linux a more pleasurable experience. This is a new series. |
 | Machine Learning explores practical applications of machine learning and deep learning from a Linux perspective. We've written reviews of more than 40 self-hosted apps. All are free and open source. |
 | New to Linux? Read our Linux for Starters series. We start right at the basics and teach you everything you need to know to get started with Linux. |
 | Alternatives to popular CLI tools showcases essential tools that are modern replacements for core Linux utilities. |
 | Essential Linux system tools focuses on small, indispensable utilities, useful for system administrators as well as regular users. |
 | Linux utilities to maximise your productivity. Small, indispensable tools, useful for anyone running a Linux machine. |
 | Surveys popular streaming services from a Linux perspective: Amazon Music Unlimited, Myuzi, Spotify, Deezer, Tidal. |
 | Saving Money with Linux looks at how you can reduce your energy bills running Linux. |
 | Home computers became commonplace in the 1980s. Emulate home computers including the Commodore 64, Amiga, Atari ST, ZX81, Amstrad CPC, and ZX Spectrum. |
 | Now and Then examines how promising open source software fared over the years. It can be a bumpy ride. |
 | Linux at Home looks at a range of home activities where Linux can play its part, making the most of our time at home, keeping active and engaged. |
 | Linux Candy reveals the lighter side of Linux. Have some fun and escape from the daily drudgery. |
 | Getting Started with Docker helps you master Docker, a set of platform as a service products that delivers software in packages called containers. |
 | Best Free Android Apps. We showcase free Android apps that are definitely worth downloading. There's a strict eligibility criteria for inclusion in this series. |
 | These best free books accelerate your learning of every programming language. Learn a new language today! |
 | These free tutorials offer the perfect tonic to our free programming books series. |
 | Linux Around The World showcases usergroups that are relevant to Linux enthusiasts. Great ways to meet up with fellow enthusiasts. |
 | Stars and Stripes is an occasional series looking at the impact of Linux in the USA. |