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Comparison · Comms
Mailu vs Stalwart
A side-by-side editorial comparison of Mailu and Stalwart — release velocity, themes, recent moves, and the top alternatives to consider.
Mailu vs Stalwart: at a glance
What is Mailu?
Mailu ships one pinned release per issue, and most of them are Roundcube's.
The 2024.06 branch releases on demand: an issue or PR comes in, a pinned version goes out, and the changelog is one or two lines. Four of the six most recent releases are webmail-driven — three Roundcube bumps in this window alone, the latest to 1.6.18 clearing a TLS-configuration warning, an earlier one to 1.6.17 closing two CVEs. The remainder are Mailu's own code: an X-Forwarded-By header fix tied to a published advisory, sieve field escaping that repaired autoreplies and closed an injection path, and two admin-UI form flow corrections.
What is Stalwart?
Stalwart is chasing mail RFCs and its own storage layer at the same time
Stalwart ships roughly weekly, and the releases divide cleanly between standards implementation and correctness work. v0.16.18 turns toward resource control — bounds on decompressed inbound DMARC and TLS report size, a cap on RocksDB block-cache memory, column families tuned per access pattern, and a queue scheduler that stops rescanning from the earliest pending event. The preceding releases added IMAP UIDONLY, UIDBATCHES and MESSAGELIMIT, plus JMAP email push and VAPID.
Mailu vs Stalwart: editorial side-by-side
Mailu
5.0COMMS
Mailu ships one pinned release per issue, and most of them are Roundcube's.
◆ Current state
The 2024.06 branch releases on demand: an issue or PR comes in, a pinned version goes out, and the changelog is one or two lines. Four of the six most recent releases are webmail-driven — three Roundcube bumps in this window alone, the latest to 1.6.18 clearing a TLS-configuration warning, an earlier one to 1.6.17 closing two CVEs. The remainder are Mailu's own code: an X-Forwarded-By header fix tied to a published advisory, sieve field escaping that repaired autoreplies and closed an injection path, and two admin-UI form flow corrections.
◆ Where it's heading
This is a maintenance branch behaving exactly as a maintenance branch should, and the pinned-version model is the product: operators get upstream security work packaged and tagged without tracking Roundcube themselves. The security items divide cleanly — most arrive from bundled components, a minority from Mailu's own code, and the project patches both on the same cadence. Nothing in this window suggests new capability is being developed on this branch.
◆ Prediction
Expect the next release to follow the same trigger: a Roundcube advisory or a client compatibility report producing a single-line changelog and a new pinned tag. Any feature work would be happening on the main version, which this feed does not cover.
Stalwart
5.0COMMS
Stalwart is chasing mail RFCs and its own storage layer at the same time
◆ Current state
Stalwart ships roughly weekly, and the releases divide cleanly between standards implementation and correctness work. v0.16.18 turns toward resource control — bounds on decompressed inbound DMARC and TLS report size, a cap on RocksDB block-cache memory, column families tuned per access pattern, and a queue scheduler that stops rescanning from the earliest pending event. The preceding releases added IMAP UIDONLY, UIDBATCHES and MESSAGELIMIT, plus JMAP email push and VAPID.
◆ Where it's heading
Two threads run through every release. One is RFC coverage across IMAP, JMAP, CalDAV and WebDAV, implemented close to the specification including drafts. The other is a long tail of protocol-conformance fixes, many of them cases where JMAP and IMAP disagreed about the same state. The newest release adds a third: memory and scheduling limits, which is what a server codebase starts doing when deployments get large enough for defaults to hurt.
◆ Prediction
Expect continued RFC additions across the JMAP and IMAP surfaces, with more of the storage-tuning work that v0.16.18 started as RocksDB deployments scale.
Alternatives to Mailu and Stalwart
Other Comms products tracked by Sparkpulse, ranked by recent ship velocity. Each card links to a full editorial trajectory and lets you pivot into a head-to-head comparison with either Mailu or Stalwart.
Proton Bridge
Proton Bridge spends its first release in ten weeks on crashes, memory bounds and dead code
Mux
Every manual control Mux ships now arrives with a Robots workflow that does it for you
Netcore Cloud
Netcore's feed remains a demand-generation channel; ten entries, zero product releases.
mailcow
mailcow's release notes are almost entirely upstream security currency.
Openfire
Openfire keeps its XMPP server current without changing what it is.
See all Mailu alternatives → · See all Stalwart alternatives →
Recent activity from Mailu and Stalwart
Latest ship moves from both products, interleaved chronologically. ⚡ = editorial spark.
- 1d agoStalwartResource limits arrive for inbound reports and RocksDB caches
- 6d agoMailuRoundcube 1.6.18 bump clears a TLS-config warning
- 8d agoStalwartIMAP gains UIDONLY, UIDBATCHES and message-limit extensions
- 16d agoStalwartJMAP delivery push arrives; strict relays stop rejecting calendar mail
- 23d agoStalwartFix-only release: JMAP semantics and a credential escalation
- 23d agoMailuAutoconfig fix for modern K-9 Mail
- 25d agoMailuRoundcube 1.6.17 closes two CVEs
- 29d agoStalwartVAPID lands for JMAP Web Push
- 1mo agoMailuSets X-Forwarded-By in response to a GHSA advisory
- 1mo agoStalwartFreeBSD support, plus OAuth scopes for IMAP, SMTP and Sieve
- 1mo agoMailuAdmin UI keeps form values on failed submit
- 1mo agoMailuEscapes sieve fields, fixing autoreplies with special characters
Frequently asked questions
What is the difference between Mailu and Stalwart?
They serve adjacent needs but don't currently overlap on shipped themes. Mailu and Stalwart are shipping at a similar cadence (velocity 5.0 vs 5.0, both within Sparkpulse's "active" band). See the at-a-glance table above for a side-by-side breakdown of velocity, recent sparks, and editorial themes.
Is Mailu better than Stalwart?
Sparkpulse doesn't pick a winner — we score release velocity, not feature parity. Mailu and Stalwart are shipping at a similar cadence (velocity 5.0 vs 5.0, both within Sparkpulse's "active" band). For your specific use case, the alternatives sections above list other Comms products to evaluate alongside.
What are the best alternatives to Mailu?
Top Mailu alternatives in Comms are ranked by recent ship velocity. Browse the "Mailu alternatives" section above for the current picks, or visit /alternatives/mailu for the full list with editorial commentary on each.
What are the best alternatives to Stalwart?
Top Stalwart alternatives in Comms are ranked by recent ship velocity. Browse the "Stalwart alternatives" section above for the current picks, or visit /alternatives/stalwart for the full list with editorial commentary on each.