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Comparison · Comms
Mailu vs Synapse
A side-by-side editorial comparison of Mailu and Synapse — release velocity, themes, recent moves, and the top alternatives to consider.
Mailu vs Synapse: at a glance
What is Mailu?
A mail server whose entire visible output is patching other people's code.
Mailu is a self-hosted mail suite shipped as a Docker compose stack, and the 2024.06.x branch shown here is its maintenance line. Every release in the window is a single-issue patch — a Roundcube bump, a CVE fix, an autoconfig tweak. The cadence looks high at ten pinned releases in five months, but each carries one change.
What is Synapse?
The reference Matrix homeserver shipping protocol work on a tight release train
Synapse is moving through the 1.156–1.158 line at roughly weekly cadence, with release candidates preceding each stable. The functional work is protocol-level: MSC4140 cancellable delayed events with per-user scheduling limits, MSC4354 sticky events exposed over MSC4186 simplified sliding sync, and stabilized ephemeral event sending. Version 1.157.0rc1 removed the deprecated MSC3861 auth delegation, and 1.157.2 was an out-of-band security release addressing several vulnerabilities rated up to high severity.
Mailu vs Synapse: editorial side-by-side
Mailu
5.0COMMS
A mail server whose entire visible output is patching other people's code.
◆ Current state
Mailu is a self-hosted mail suite shipped as a Docker compose stack, and the 2024.06.x branch shown here is its maintenance line. Every release in the window is a single-issue patch — a Roundcube bump, a CVE fix, an autoconfig tweak. The cadence looks high at ten pinned releases in five months, but each carries one change.
◆ Where it's heading
Most of what Mailu ships is downstream maintenance of its bundled components, Roundcube above all, which drove three of these ten releases. The project's own work here is defensive: escaping user-controlled fields in generated sieve scripts, setting X-Forwarded-By, adapting to Microsoft's new autodiscover. This is a product in steady-state operation, where the release notes track what upstream broke rather than what Mailu decided to build.
◆ Prediction
The next pinned release will most likely be another Roundcube or Alpine bump, since component upgrades triggered half the releases here. These entries say nothing about what is happening on the main branch.
Synapse
5.0COMMS
The reference Matrix homeserver shipping protocol work on a tight release train
◆ Current state
Synapse is moving through the 1.156–1.158 line at roughly weekly cadence, with release candidates preceding each stable. The functional work is protocol-level: MSC4140 cancellable delayed events with per-user scheduling limits, MSC4354 sticky events exposed over MSC4186 simplified sliding sync, and stabilized ephemeral event sending. Version 1.157.0rc1 removed the deprecated MSC3861 auth delegation, and 1.157.2 was an out-of-band security release addressing several vulnerabilities rated up to high severity.
◆ Where it's heading
Development tracks the Matrix spec process directly — features arrive as MSCs graduate, and deprecated experimental paths are removed once replacements stabilize. Sliding sync is the load-bearing effort, with sticky events and ephemeral sending both being routed through it. The security release and the config regression that followed 1.157.0 show the cost of that cadence: fast lines need fast patches.
◆ Prediction
Expect the 1.158 line to continue folding MSCs into sliding sync, and further removal of experimental_features flags whose MSCs have stabilized, following the MSC3861 precedent.
Alternatives to Mailu and Synapse
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 Synapse.
Chatwoot
Chatwoot added voice, then pointed its AI agent at the tickets it already resolved.
Roundcube
After four years, Roundcube 1.7 lands — and the release stream is otherwise all CVEs
Signal Desktop
Signal's beta train is quietly handing group admins real moderation powers.
Notion
Notion is turning itself into the place other companies' agents come to work.
Slack
Slack's app platform is being rebuilt around agents, with the SDKs clearing old ground behind it.
See all Mailu alternatives → · See all Synapse alternatives →
Recent activity from Mailu and Synapse
Latest ship moves from both products, interleaved chronologically. ⚡ = editorial spark.
- 21h agoSynapse1.158 release candidate opens
- 3d agoSynapseOut-of-band security release for federated homeservers
- 5d agoMailuAutoconfig fix for modern K-9 Mail
- 7d agoMailuRoundcube 1.6.17 closes two CVEs
- 8d agoSynapseConfig regression on falsy experimental_features fixed
- 9d agoSynapseCancellable delayed events reach stable
- 12d agoMailuSets X-Forwarded-By in response to a GHSA advisory
- 15d agoSynapseMSC3861 auth delegation removed in 1.157 RC
- 24d agoSynapseSticky events exposed over simplified sliding sync
- 26d agoMailuAdmin UI keeps form values on failed submit
- 1mo agoMailuEscapes sieve fields, fixing autoreplies with special characters
- 2mo agoMailuRoundcube 1.6.16 and carddav 5.1.3 close CVE-2026-49217
Frequently asked questions
What is the difference between Mailu and Synapse?
They serve adjacent needs but don't currently overlap on shipped themes. Mailu and Synapse 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 Synapse?
Sparkpulse doesn't pick a winner — we score release velocity, not feature parity. Mailu and Synapse 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 Synapse?
Top Synapse alternatives in Comms are ranked by recent ship velocity. Browse the "Synapse alternatives" section above for the current picks, or visit /alternatives/synapse for the full list with editorial commentary on each.