FOSDEM 2026 - Stalwart: Can Open Source do Gmail-scale Email?

Marginal Gains: Major Impact | Stalwart Labs

In professional cycling, the concept of marginal gains became famous through Team Sky. Rather than chasing dramatic breakthroughs, they focused on making hundreds of small improvements: slightly better bike fit, marginally lighter components, improved sleep, cleaner nutrition. None of these changes mattered much on their own, but together they reshaped performance—and helped dominate the sport for years.

JMAP for Calendars, Contacts and Files now in Stalwart | Stalwart Labs

After four years of development, we’re thrilled to announce a major milestone in the evolution of Stalwart — the full implementation of JMAP for Calendars, Contacts,File Storage, and Sharing. With this release, Stalwart becomes the first JMAP server to fully support the entire family of JMAP collaboration protocols, marking a new era for open, efficient, and elegant groupware.

Security at the Core: Stalwart completes Second Security Audit | Stalwart Labs

At Stalwart Labs, security is at the heart of everything we build. As part of our ongoing commitment to delivering a trustworthy email and collaboration server, we recently completed our second independent security audit, conducted by Radically Open Security. Our previous audit took place exactly two years ago, in 2023 — and with significant changes to our codebase since then, a fresh and thorough assessment was essential.

Stalwart Joins GitHub's Open Source Secure Fund | Stalwart Labs

We're excited to announce that Stalwart has been selected to participate in Session 2 of GitHub's Open Source Secure Fund (OSSF), a prestigious program designed to enhance security across the open source ecosystem. This recognition represents not only an acknowledgment of Stalwart's growing importance in the email infrastructure space but also our commitment to maintaining the highest security standards.

Introducing Virtual Queues and Strategy-Driven Delivery in Stalwart MTA | Stalwart Labs

At Stalwart Labs, we're constantly working to evolve and improve our software based on real-world feedback. Today, we're excited to announce a major enhancement to the queueing system in Stalwart MTA, designed to meet the needs of some of our busiest users—those delivering millions of messages per day.

The Future of Stalwart: Webmail, Roadmap, and Beyond | Stalwart Labs

Since we officially started developing Stalwart on September 4th, 2021, we've come a long way in establishing a powerful and versatile open-source mail and collaboration server. The very first commit, made on October 3rd, 2021, was to the mail-parser Rust crate, a fundamental component upon which Stalwart was built. It set the tone for our relentless pursuit of secure, reliable, and performant software.

Introducing Calendars, Contacts and Files in Stalwart | Stalwart Labs

We’re excited to announce the release of Stalwart v0.12, a significant milestone that evolves Stalwart from a powerful mail server into a complete, integrated communication and collaboration platform. This release delivers one of the most anticipated features from our community: native support for calendars, contacts, and file storage—all built directly into the server, with no need for third-party integrations.

Stalwart Receives NLNet Grant to Build Collaboration Server | Stalwart Labs

We’re happy to announce that Stalwart Labs has been awarded a new grant from the NGI0 Core Fund, established by NLnet with financial support from the European Commission’s Next Generation Internet programme. This funding will support the development of essential collaboration features, marking a major milestone in Stalwart’s evolution from a modern email server into a complete, self-hosted collaboration platform.

OpenID Connect Integration is now Open Source | Stalwart Labs

We are happy to announce that third-party OpenID Connect (OIDC) authentication support has now been open-sourced under the AGPL-3.0 license in Stalwart Mail Server version 0.11.5. This means that users can now configure Stalwart Mail Server to authenticate against external OIDC providers, such as Keycloak, without requiring an Enterprise subscription.