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Robust, secure, and scalable message storage, expertly handling all modern email protocols.

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JMAP Server

Embracing modern email with JMAP.

JMAP (JSON Meta Application Protocol) is a contemporary protocol designed to be a modern replacement for IMAP, enhancing the way email clients sync with mail servers. Unlike its predecessor, JMAP uses JSON to structure data and HTTP for its transport layer, making it more efficient and suitable for today's mobile and web-based environments. Stalwart stands out as one of the few email servers on the market that fully implements JMAP, providing users with a cutting-edge, streamlined email syncing experience.

  • JMAP Core full support.
  • JMAP Mail full support.
  • JMAP over WebSockets extension.
  • JMAP for Sieve Scripts extension.
  • JMAP for Quotas extension.
  • JMAP Blob Management extension.

IMAP4 & POP3 server

Broad compatibility with modern and legacy protocols.

Stalwart seamlessly supports both cutting-edge and legacy email protocols, including the latest IMAP4 revision 2, the established IMAP4 revision 1, and POP3 for older clients. Additionally, Stalwart implements dozens of IMAP4 extensions, enhancing functionality and user experience across a variety of email client software. This dual focus on the future and the past allows Stalwart to offer a versatile and robust email server solution, capable of meeting diverse user needs in a changing technological landscape.

  • IMAP4rev2 full compliance.
  • IMAP4rev1 compatible.
  • POP3 support.
  • CONDSTORE and QRESYNC for mailbox synchronization.
  • Dozens of IMAP4 extensions.

Sieve scripting

Enhanced automation with Sieve scripting.

Stalwart offers comprehensive support for Sieve (a scripting language designed for filtering and managing email) as well all registered extensions, ensuring a wide range of capabilities for users to customize their email handling. The built-in Sieve interpreter is not only fast but also secure, featuring sandboxed code execution to protect against security vulnerabilities. Additionally, users can conveniently manage their Sieve scripts either through the included ManageSieve server or via JMAP for Sieve Scripts, providing flexible and accessible options for script management.

  • Sieve scripting support.
  • All extensions supported.
  • ManageSieve server.
  • JMAP for Sieve Scripts extension.


Elevating your email experience.

Stalwart is engineered to be a feature-rich email server solution, delivering advanced capabilities that cater to diverse needs and enhance user experience. From seamless security measures to extensive customization options, each integrated feature ensures a comprehensive, efficient, and secure communication platform. Stalwart's versatile architecture not only simplifies administration but also scales effectively to meet the demands of any organization.

  • Built-in full-text search available in 17 languages.
  • Automatic account configuration and discovery.
  • Automatic TLS certificate provisioning with ACME.
  • E-mail aliases, mailing lists, sub-addressing and catch-all addresses support.
  • OpenTelemetry support.
  • OAuth 2.0 authorization code and device authorization flows.
  • Disk quotas.


Robust security and encryption.

Stalwart is designed with a robust security framework to ensure the highest level of protection for your communications. The platform incorporates advanced security features and encryption technologies that safeguard data both in transit and at rest. With proactive measures like host blocking and rate limiting, along with rigorously tested access controls, Stalwart ensures a secure and reliable email environment. Its memory-safe architecture and comprehensive security audits further underline its commitment to maintaining strong defenses against evolving threats.

  • Encryption at rest with S/MIME or OpenPGP.
  • Automated blocking of hosts (aka fail2ban).
  • Access Control Lists (ACLs).
  • Rate and concurrency limiting.
  • Memory safe.
  • Security audited.

Flexible Storage

Diverse storage and authentication options for every need.

Stalwart offers a versatile and powerful range of storage and authentication options designed to meet various needs and technical requirements. Its flexible architecture supports everything from fast local data storage to extensive distributed storage, enabling both high performance and scalability. Whether you require robust database storage, efficient caching, specialized blob storage, or advanced search capabilities, Stalwart provides the right tools to optimize and enhance your data management strategies.

  • FoundationDB for distributed data storage.
  • RocksDB and SQLite for fast, local data storage.
  • PostgreSQL, MySQL and MariaDB for relational data storage
  • Redis for caching and lookup storage.
  • S3-Compatible for distributed blob storage.
  • Filesystem for local blob storage.
  • ElasticSearch for full-text search.
  • LDAP for authentication and authorization.

Web-based admin

Effortless web-based management at your fingertips.

Stalwart provides a streamlined management experience through its comprehensive web-based administration interface. This platform eliminates the need for traditional server management methods, such as using text editors or SSH access, by enabling full control over the mail server directly from a web browser. The webadmin is designed as a Single Page Application (SPA), ensuring a swift and responsive user experience. From intricate configuration adjustments to basic account management, all aspects of the server can be effortlessly handled online, providing both administrators and users with a powerful, efficient tool for managing their email environment.

  • Account, domain, group and mailing list management.
  • 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.

Built to scale

Seamless scalability for millions of mailboxes.

Unlike traditional mail servers, which often rely on coordinators and proxies to scale and are limited by ancient storage formats like Maildir that tie user accounts to a single server, Stalwart is engineered to scale effortlessly from the start. When paired with modern storage backends such as FoundationDB, Stalwart can seamlessly handle millions of mailboxes. This design not only eliminates the need for complex scaling solutions but also ensures robust performance and reliability across extensive email infrastructures.

  • Seamless load balancing and fault tolerance.
  • Node autodiscovery, streamlining network expansion.
  • Network partition-tolerant failure detection.
  • Simplified architecture without coordinators or proxies.