What is Stalwart used for?

Stalwart is an all-in-one mail and collaboration server written in Rust that speaks JMAP, IMAP, POP3, SMTP, CalDAV, CardDAV and WebDAV. It is a good fit for self-hosting email and calendars, and replacing a multi-component mail stack.

Is Stalwart open source?

Yes. Stalwart is open source. Its source code is on GitHub at stalwartlabs/stalwart and is written mainly in Rust.

Yes. Stalwart is open source, so the software itself is free to use. Paid plans are also available, starting at $2.40 per seat per year.

Can I self-host Stalwart?

Yes. Stalwart can be self-hosted on your own server or infrastructure.

What is Stalwart an alternative to?

Stalwart is an open-source alternative to Google Workspace, Gmail, Fastmail and Zoho Mail. Other open-source alternatives to Google Workspace include Mailcow, Mail-in-a-Box and Forward Email.

Is Stalwart actively maintained?

Yes. The most recent commit to Stalwart was on 2 October 2026, and the latest release is v0.16.24, published on 27 September 2026. The project has 15k stars on GitHub.

Stalwart: open-source alternative to Google Workspace, Gmail

About Stalwart

Stalwart is an open-source mail and collaboration server written in Rust and designed to be secure, fast, robust and scalable. It supports JMAP, IMAP4, POP3, SMTP, CalDAV, CardDAV and WebDAV, so a single server can handle email, calendars, contacts and file storage.

On the email side it offers JMAP for Mail and Sieve, IMAP4rev2 and IMAP4rev1 with ManageSieve, and POP3. The SMTP server includes DMARC, DKIM, SPF and ARC for message authentication, transport security through DANE, MTA-STS and TLS reporting, automated DKIM key rotation, throttling and filtering rules, sieve scripting and milter integration, and distributed virtual queues.

The collaboration features cover CalDAV and JMAP for Calendars, CardDAV and JMAP for Contacts, and WebDAV and JMAP for File Storage, with fine-grained sharing through WebDAV ACL and JMAP Sharing. A built-in spam and phishing filter includes a rule set and LLM-driven message analysis. It is self-hosted software that administrators run on their own servers.

Key features

JMAP, IMAP4, POP3 and SMTP servers
Calendars, contacts and file storage
DMARC, DKIM, SPF and ARC support
Built-in spam and phishing filter
Fine-grained sharing and access controls
Written in Rust for speed and safety

Good fit for

→Self-hosting email and calendars
→Replacing a multi-component mail stack

Built with: Rust
Tags: mail-server; jmap; imap; smtp; caldav; carddav; rust; self-hosted

Stalwart: questions and answers

What is Stalwart used for?: Stalwart is an all-in-one mail and collaboration server written in Rust that speaks JMAP, IMAP, POP3, SMTP, CalDAV, CardDAV and WebDAV. It is a good fit for self-hosting email and calendars, and replacing a multi-component mail stack.
Is Stalwart open source?: Yes. Stalwart is open source. Its source code is on GitHub at stalwartlabs/stalwart and is written mainly in Rust.
Is Stalwart free?: Yes. Stalwart is open source, so the software itself is free to use. Paid plans are also available, starting at $2.40 per seat per year.
Can I self-host Stalwart?: Yes. Stalwart can be self-hosted on your own server or infrastructure.
What is Stalwart an alternative to?: Stalwart is an open-source alternative to Google Workspace, Gmail, Fastmail and Zoho Mail. Other open-source alternatives to Google Workspace include Mailcow, Mail-in-a-Box and Forward Email.
Is Stalwart actively maintained?: Yes. The most recent commit to Stalwart was on 2 October 2026, and the latest release is v0.16.24, published on 27 September 2026. The project has 15k stars on GitHub.