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Comparison · Comms
Stalwart vs Synapse
A side-by-side editorial comparison of Stalwart and Synapse — release velocity, themes, recent moves, and the top alternatives to consider.
Stalwart vs Synapse: at a glance
What is Stalwart?
Stalwart races to implement the newest email standards across its all-in-one server
Stalwart is an open-source, all-in-one mail and collaboration server (SMTP/IMAP/JMAP/CalDAV) shipping a fast 0.16.x point-release train. Recent releases are dominated by standards implementation and protocol-conformance work, layered over steady security hardening and a long tail of targeted bug fixes.
What is Synapse?
Synapse holds its biweekly cadence, grinding through Matrix spec MSCs
Synapse is the reference Matrix homeserver, shipping on a steady two-week release train. Recent work centers on Simplified Sliding Sync (MSC4186), sticky events, cancellable delayed events, and a preview-URL capabilities API, alongside a run of federation and to-device stability fixes. This is maintenance-heavy engineering: paired rc/stable releases, a mid-May CVE security patch in 1.152.1, and Debian 12 packaging now being retired.
Stalwart vs Synapse: editorial side-by-side
Stalwart
5.0COMMS
Stalwart races to implement the newest email standards across its all-in-one server
◆ Current state
Stalwart is an open-source, all-in-one mail and collaboration server (SMTP/IMAP/JMAP/CalDAV) shipping a fast 0.16.x point-release train. Recent releases are dominated by standards implementation and protocol-conformance work, layered over steady security hardening and a long tail of targeted bug fixes.
◆ Where it's heading
The product is doubling down on being the most standards-complete self-hosted mail server: early DKIM2 and DMARCbis authentication, IDN support, encryption-at-rest for S/MIME, and a sustained push to pass the JMAP test suite. Security hardening runs alongside — DANE downgrade-attack defenses, auto-ban fixes, binary attestation on every build.
◆ Prediction
Expect continued rapid 0.16.x releases advancing draft email-authentication standards and JMAP conformance; a larger 0.17 or 1.0 milestone becomes likely once the JMAP suite fully passes and the DKIM2/DMARCbis drafts stabilize.
Synapse
5.0COMMS
Synapse holds its biweekly cadence, grinding through Matrix spec MSCs
◆ Current state
Synapse is the reference Matrix homeserver, shipping on a steady two-week release train. Recent work centers on Simplified Sliding Sync (MSC4186), sticky events, cancellable delayed events, and a preview-URL capabilities API, alongside a run of federation and to-device stability fixes. This is maintenance-heavy engineering: paired rc/stable releases, a mid-May CVE security patch in 1.152.1, and Debian 12 packaging now being retired.
◆ Where it's heading
The arc is incremental spec conformance, not new direction. Sliding Sync and appservice/ephemeral-event plumbing are maturing toward Matrix 1.15 requirements, with repeated fix-and-stabilize cycles (one Sliding Sync change was reverted for performance and re-landed). Expect continued MSC pickups and hardening rather than architectural change.
◆ Prediction
The next release likely stabilizes more Sliding Sync and sticky-event behavior and continues trimming legacy packaging, arriving as another rc-then-stable pair within roughly two weeks.
Alternatives to Stalwart 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 Stalwart or Synapse.
Twilio
Twilio goes enterprise-programmable: OAuth2 org APIs, roles, SCIM, HIPAA-ready messaging
Canary Mail
Canary Mail runs synchronized cross-platform releases, mostly fixes with light AI-compose tuning.
SimpleX Chat
SimpleX's v7.0 beta grows a private messenger into a public-channel network
Telnyx
Telnyx is bending its telecom stack toward autonomous voice agents.
Melp
Melp's feed is SEO comparison content, not a product changelog
See all Stalwart alternatives → · See all Synapse alternatives →
Recent activity from Stalwart and Synapse
Latest ship moves from both products, interleaved chronologically. ⚡ = editorial spark.
- 6h agoSynapseSticky events over Sliding Sync; appservice EDUs stabilized
- 1d agoStalwartDKIM2 and DMARCbis email-authentication support
- 7d agoSynapseRelease candidate for 1.156.0
- 12d agoStalwartEncryption-at-rest for S/MIME, Redis Sentinel backend
- 16d agoStalwartIDN support and JMAP test-suite conformance
- 21d agoSynapseFederation to-device fixes; drops Debian 12 packaging
- 28d agoSynapseRelease candidate for 1.155.0
- 1mo agoSynapseMSC4452 preview-URL capabilities API
- 1mo agoSynapseRelease candidate for 1.154.0
Frequently asked questions
What is the difference between Stalwart and Synapse?
They serve adjacent needs but don't currently overlap on shipped themes. Stalwart 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 Stalwart better than Synapse?
Sparkpulse doesn't pick a winner — we score release velocity, not feature parity. Stalwart 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 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.
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.