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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

FeatureStalwartSynapse
SectorCommsComms
Velocity score5.05.0
Sparks · 30d00
Top themesmail-server, jmap, imap, rfc-compliancematrix-protocol, federation, homeserver, security-releases
Last editorial update20h ago7d ago
WebsiteVisit →Visit →

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.

Read the full Stalwart trajectory →

What is Synapse?

Synapse alternates release candidates with security patches on a tight two-week cycle

The feed is a straight release stream on a roughly two-week rhythm: a release candidate, a final, then point releases as needed. Recent substance sits in 1.157.0 — limits on scheduled delayed events, backward movement of fully read markers, time filters on the user-redaction admin API, and a configuration option to stop presence routing between users who merely share a room. 1.157.2 followed as a security release covering eleven advisories, six of them high severity.

Read the full Synapse trajectory →

Stalwart vs Synapse: editorial side-by-side

S5.0

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.

S
Synapse
COMMS
5.0

Synapse alternates release candidates with security patches on a tight two-week cycle

◆ Current state

The feed is a straight release stream on a roughly two-week rhythm: a release candidate, a final, then point releases as needed. Recent substance sits in 1.157.0 — limits on scheduled delayed events, backward movement of fully read markers, time filters on the user-redaction admin API, and a configuration option to stop presence routing between users who merely share a room. 1.157.2 followed as a security release covering eleven advisories, six of them high severity.

◆ Where it's heading

Development is tracking the Matrix specification process rather than a product roadmap of its own — most features arrive as implementations of numbered MSCs, several contributed from outside. The operational theme underneath is load and blast radius: presence exclusion, caps on delayed events, and locked sliding-sync connections all reduce what a busy homeserver has to carry. Security handling is centralized and batched, shipped as one patch release rather than trickled out.

◆ Prediction

Expect 1.159.0 to follow its release candidate within roughly a week, continuing the MSC-implementation pattern. The recent removal of deprecated auth delegation suggests more cleanup of experimental configuration in the coming releases.

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.

See all Stalwart alternatives → · See all Synapse alternatives →

Recent activity from Stalwart and Synapse

Latest ship moves from both products, interleaved chronologically. ⚡ = editorial spark.

  1. 1d agoStalwartResource limits arrive for inbound reports and RocksDB caches
  2. 7d agoSynapsev1.159.0rc1
  3. 8d agoStalwartIMAP gains UIDONLY, UIDBATCHES and message-limit extensions
  4. 14d agoSynapsev1.158.0
  5. 16d agoStalwartJMAP delivery push arrives; strict relays stop rejecting calendar mail
  6. 19d agoSynapsev1.158.0rc1
  7. 21d agoSynapseSynapse 1.157.2 patches 11 security advisories, six high severity
  8. 23d agoStalwartFix-only release: JMAP semantics and a credential escalation
  9. 27d agoSynapseSynapse 1.157.1 fixes falsy experimental_features config regression
  10. 28d agoSynapseSynapse 1.157.0 adds delayed-event limits and QR sign-in support
  11. 29d agoStalwartVAPID lands for JMAP Web Push
  12. 1mo agoStalwartFreeBSD support, plus OAuth scopes for IMAP, SMTP and Sieve

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.