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Proton Bridge vs Stalwart

A side-by-side editorial comparison of Proton Bridge and Stalwart — release velocity, themes, recent moves, and the top alternatives to consider.

Shared themes:imap

Proton Bridge vs Stalwart: at a glance

FeatureProton BridgeStalwart
SectorCommsComms
Velocity score2.55.0
Sparks · 30d00
Top themesemail, imap, privacy, maintenancemail-server, jmap, imap, rfc-compliance
Last editorial update18h ago23h ago
WebsiteVisit →Visit →

What is Proton Bridge?

Proton Bridge spends its first release in ten weeks on crashes, memory bounds and dead code

v3.26.0 is a maintenance cut. The user-visible items are a macOS 27 crash fix, bounded CPU and memory in the Gluon RFC parser, deletion of orphaned unencrypted vaults once keychain access returns, and a meta+W shortcut. The rest is internal: two unused subsystems removed from go-proton-api, two Go toolchain bumps, gomock swapped for uber-go/mock, and June and July vulnerability patches folded in.

Read the full Proton Bridge trajectory →

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 →

Proton Bridge vs Stalwart: editorial side-by-side

P2.5

Proton Bridge spends its first release in ten weeks on crashes, memory bounds and dead code

◆ Current state

v3.26.0 is a maintenance cut. The user-visible items are a macOS 27 crash fix, bounded CPU and memory in the Gluon RFC parser, deletion of orphaned unencrypted vaults once keychain access returns, and a meta+W shortcut. The rest is internal: two unused subsystems removed from go-proton-api, two Go toolchain bumps, gomock swapped for uber-go/mock, and June and July vulnerability patches folded in.

◆ Where it's heading

Releases arrive in long gaps — ten weeks since v3.25.0 — and each one bundles a quarter of dependency hygiene with a handful of IMAP correctness fixes. The recurring theme is RFC 3501 conformance and resource bounds in the mail parser rather than new capability, which is what a local IMAP shim for an encrypted mailbox is supposed to look like.

◆ Prediction

Given the pattern of shipping OS-compatibility fixes shortly after a macOS release, the next cut is likely another maintenance bundle timed to whatever the current macOS version breaks.

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.

Alternatives to Proton Bridge 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 Proton Bridge or Stalwart.

See all Proton Bridge alternatives → · See all Stalwart alternatives →

Recent activity from Proton Bridge and Stalwart

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

  1. 1d agoStalwartResource limits arrive for inbound reports and RocksDB caches
  2. 1d agoProton BridgeBridge 3.26.0: macOS 27 crash fix and bounded RFC parser resources
  3. 8d agoStalwartIMAP gains UIDONLY, UIDBATCHES and message-limit extensions
  4. 16d agoStalwartJMAP delivery push arrives; strict relays stop rejecting calendar mail
  5. 23d agoStalwartFix-only release: JMAP semantics and a credential escalation
  6. 29d agoStalwartVAPID lands for JMAP Web Push
  7. 1mo agoStalwartFreeBSD support, plus OAuth scopes for IMAP, SMTP and Sieve
  8. 2mo agoProton BridgeBridge 3.25.0: IMAP and sync fixes bundled with dependency updates
  9. 3mo agoProton BridgeBridge 3.24.2 patch with a single-line note
  10. 4mo agoProton BridgeBridge 3.24.1 patch with a single-line note
  11. 4mo agoProton BridgeBridge 3.24.0 Nescio feature cut
  12. 4mo agoProton BridgeBridge 3.23.1 patch on the Margit line

Frequently asked questions

What is the difference between Proton Bridge and Stalwart?

Both compete on the same themes — imap — within Comms. Stalwart is currently shipping more aggressively (velocity 5.0 vs 2.5), with 0 editorial sparks in the last 30 days against 0. See the at-a-glance table above for a side-by-side breakdown of velocity, recent sparks, and editorial themes.

Is Proton Bridge better than Stalwart?

Sparkpulse doesn't pick a winner — we score release velocity, not feature parity. Stalwart is currently shipping more aggressively (velocity 5.0 vs 2.5), with 0 editorial sparks in the last 30 days against 0. For your specific use case, the alternatives sections above list other Comms products to evaluate alongside.

What are the best alternatives to Proton Bridge?

Top Proton Bridge alternatives in Comms are ranked by recent ship velocity. Browse the "Proton Bridge alternatives" section above for the current picks, or visit /alternatives/proton-bridge 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.