Stalwart - 2026 Pricing, Features, Reviews & Alternatives

Stalwart Mail is an open-source communication platform that integrates modern email protocols with collaboration tools in a unified solution. The software provides comprehensive support for JMAP, IMAP four, POP three, SMTP and WebDAV protocols. It consolidates traditional email infrastructure components such as the mail transfer agent, message store, spam filter, calendar and contact management into a single executable with a unified configuration.

The solution features a comprehensive security framework that includes encryption at rest with S/MIME or OpenPGP, transport security through DANE, MTA-STS and TLS reporting, and automatic certificate provisioning via ACME. Granular access control lists, rate limiting and fail two ban protection prevent unauthorized access. Spam and phishing defenses rely on DMARC, DKIM, SPF and ARC for sender authentication, statistical spam classification with automatic training, DNS blocklist verification and phishing protection against homographic and spoofing attacks. Collaboration capabilities extend to calendar and event scheduling with free and busy support, contact management and file storage with secure sharing. Administrative tools include enhanced Sieve scripting, dynamic configuration rules and full-text search across seventeen languages.

The architecture accommodates integration with various storage and authentication backends, offering deployment flexibility. When paired with modern storage engines such as FoundationDB, the system scales to handle millions of mailboxes without requiring coordinators or proxies. Features such as node autodiscovery, partition-tolerant failure detection and load balancing ensure continuous operation.