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Stalwart Blog

Marginal Gains: Major Impact

- 5 min read
Mauro D.
Mauro D.
Project Maintainer

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.

Software systems, especially large distributed ones, work much the same way. Rarely does a single feature transform everything overnight. More often, real progress comes from careful attention to small details: shaving latency here, reducing contention there, simplifying a hot path, rethinking a data structure.

Stalwart v0.15 is very much a release in this spirit. It does not introduce a long list of headline features. Instead, it is the result of revisiting core subsystems—spam filtering, search, storage, and data access—and making many targeted improvements that, together, have a significant impact on performance, reliability, and usability.

JMAP for Calendars, Contacts and Files now in Stalwart

- 4 min read
Mauro D.
Mauro D.
Project Maintainer

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

- 3 min read
Mauro D.
Mauro D.
Project Maintainer

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

- 6 min read
Mauro D.
Mauro D.
Project Maintainer

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

- 4 min read
Mauro D.
Mauro D.
Project Maintainer

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.

This update is the result of valuable input from operators managing large-scale mail infrastructure. Many reported a recurring issue: when message volumes spiked, low-priority traffic, such as DMARC aggregate reports and Delivery Status Notifications (DSNs), would often compete with or delay the delivery of legitimate user mail. Since all messages were processed through a single delivery queue, these traffic types were treated equally, regardless of urgency or purpose.