Why it exists

Running your own mail server used to mean stitching together half a dozen components — Postfix (MTA), Dovecot (IMAP), Rspamd/SpamAssassin (spam), a calendar server, a contacts server, a file server — each with its own configuration quirks, failure modes and admin UI. Stalwart collapses all of that into one platform: fewer services to deploy, one configuration to learn, one place to look when something needs attention, and a smaller attack surface. It's written in memory-safe Rust, was designed for clustering from day one, and supports every standard protocol so your existing clients keep working.

Main features

• Email for every client — modern JMAP for new apps, full IMAP4/POP3 for everything else, and SMTP for delivery. Works with Thunderbird, Outlook, Apple Mail, mobile clients.
• MTA — sender authentication (DKIM, SPF, DMARC, ARC), clustered queues, per-domain routing, no separate relay tier.
• Integrated anti-spam & anti-phishing — statistical classifier with automatic training, DNSBL checking, sender reputation (by IP/ASN/domain), greylisting, spam traps, Pyzor, phishing defenses (homograph URLs, spoofing), trusted-reply tracking, optional LLM-driven message analysis — all inside the same product, scoring mail at SMTP time.
• Collaboration — CalDAV calendars (invitations, free/busy), CardDAV contacts, WebDAV file storage and sharing — plus modern JMAP equivalents — all sharing one identity layer with the mail.
• Security as a default — mailboxes encrypted at rest with the user's own S/MIME certificate or OpenPGP key (even an operator with disk access can't read them); DANE, MTA-STS, TLS reporting; automatic TLS via ACME; automated DKIM key rotation; granular ACLs, rate limiting, IP banning; independently security-audited.
• Built to scale — any node serves any protocol, peer-to-peer cluster coordination (Zenoh) with optional Kafka/Redpanda/NATS/Redis coordinators, distributed MTA queues, read replicas, sharded blob storage; Kubernetes/Mesos/Swarm orchestration. Designed for millions of mailboxes.
• Fits your existing stack — pluggable storage (RocksDB, FoundationDB, PostgreSQL, MySQL, SQLite, S3, Azure Blob, Redis), full-text search in 17 languages (internal or via Meilisearch/ElasticSearch/OpenSearch/PostgreSQL), auth via LDAP, OIDC, SQL or built-in (with 2FA, app passwords, API keys), Sieve scripting, automated DNS management (Cloudflare, Route53, …), web admin + CLI.

Who it's for

• Self-hosters who want a real mail server (not just webmail) without maintaining a Postfix/Dovecot/Rspamd zoo.
• Small and medium organizations wanting mail + calendars + contacts + files on their own infrastructure.
• Hosting providers and MSPs — multi-tenant, clusterable, and honestly priced (free Community Edition, Enterprise for the extras).
• Security-minded teams: encrypted-at-rest mailboxes and a modern, memory-safe codebase are rare in mail.

How it compares

Useful links

• Website: https://stalw.art/
• Docs: https://stalw.art/docs
• GitHub: https://github.com/stalwartlabs/stalwart
• Editions & pricing: https://stalw.art/editions

Notes

• 15,000+ GitHub stars — arguably the most exciting Rust infrastructure project in the mail space right now.
• Available as a single binary or Docker; the "install in minutes" claim is credible and the web dashboard is genuinely good.
• If you've ever said "self-hosting email is impossible", Stalwart is the strongest counter-argument in years.