Stalwart Mail Server
Open-source mail and collaboration server combining email, calendars, contacts and file in
Stalwart Mail Server is an open-source, Rust-native platform that combines email, calendars, contacts, and shared file storage on a single server, replacing the separate MTA, message store, spam filter, and DAV servers typically required. It natively supports JMAP, IMAP4, POP3, SMTP, CalDAV, CardDAV, and WebDAV, and includes spam and phishing filtering at SMTP time using a statistical classifier, DNSBL checking, sender reputation, and optional LLM-driven analysis. It can run as a single node or as a cluster, with pluggable storage backends (RocksDB, FoundationDB, PostgreSQL, MySQL, SQLite, S3, Azure Blob), delegated search (Meilisearch, Elasticsearch, OpenSearch), and authentication via LDAP, OIDC, SQL, or a built-in directory.
Stalwart integrates with existing infrastructure through DNS providers (Cloudflare, Route 53, Google Cloud DNS, and others), external anti-spam tools (SpamAssassin, RSPAMD via Milter or MTA Hooks), observability stacks (OpenTelemetry, Prometheus, webhooks), and orchestrators (Kubernetes, Mesos, Docker Swarm). It is dual-licensed: a free Community edition under AGPL-3.0 and a commercial Enterprise edition with a 30-day trial, licensed per mailbox on annual or monthly billing, with tiered rates that decrease as mailbox counts grow. Premium Support is included at 150 mailboxes and above.
12 alternatives to Stalwart Mail Server
Ranked by how well each tool replaces Stalwart Mail Server: shared features, audience, price and popularity.
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