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Comparison · Comms
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.
Proton Bridge vs Stalwart: at a glance
What is Proton Bridge?
Proton Bridge is in pure maintenance: security patches and RFC compliance fixes dominate 2026
Proton Bridge has shipped six releases since February, none of which introduce user-visible features. The work is security vulnerability patching (August 2026 CVEs), RFC3501 IMAP compliance fixes, Go toolchain upgrades, and bug fixes in the Gluon IMAP server component. The v3.24.0 cycle added IMAP connection limiting and buffer pooling for message decryption — the most substantive user-affecting work in the reviewed period.
What is Stalwart?
Stalwart adds full SCIM v2 provisioning and 24-language calendar support as its standards coverage extends further than most commercial mail servers.
Stalwart is maintaining a weekly-or-faster release cadence, with alternating feature releases and dense bug-fix releases. The v0.16.20 release landed full SCIM v2 (Enterprise) including cursor-based pagination and the IPSIE lifecycle profile, conference links in calendar invites, and 24 new calendar interface translations. Below the feature line, the project is steadily closing correctness gaps across JMAP, CalDAV, IMAP, and MTA — many of them edge-case RFC compliance issues.
Proton Bridge vs Stalwart: editorial side-by-side
Proton Bridge
5.0COMMS
Proton Bridge is in pure maintenance: security patches and RFC compliance fixes dominate 2026
◆ Current state
Proton Bridge has shipped six releases since February, none of which introduce user-visible features. The work is security vulnerability patching (August 2026 CVEs), RFC3501 IMAP compliance fixes, Go toolchain upgrades, and bug fixes in the Gluon IMAP server component. The v3.24.0 cycle added IMAP connection limiting and buffer pooling for message decryption — the most substantive user-affecting work in the reviewed period.
◆ Where it's heading
Proton Bridge is in a sustain phase. The Gluon subsystem is getting more robust error reporting, CPU/memory bounds on the RFCP parser, and feature flags for controlled rollouts — signals of hardening a component that has historically caused reliability issues. No new end-user capabilities are visible in the roadmap from the changelog alone.
◆ Prediction
The next release will likely be another security or compatibility patch. Meaningful feature expansion would require Proton to signal a direction change for Bridge publicly, and nothing in this changelog points toward one.
Stalwart
6.3COMMS
Stalwart adds full SCIM v2 provisioning and 24-language calendar support as its standards coverage extends further than most commercial mail servers.
◆ Current state
Stalwart is maintaining a weekly-or-faster release cadence, with alternating feature releases and dense bug-fix releases. The v0.16.20 release landed full SCIM v2 (Enterprise) including cursor-based pagination and the IPSIE lifecycle profile, conference links in calendar invites, and 24 new calendar interface translations. Below the feature line, the project is steadily closing correctness gaps across JMAP, CalDAV, IMAP, and MTA — many of them edge-case RFC compliance issues.
◆ Where it's heading
Stalwart is building toward parity with commercial enterprise mail servers on identity federation and provisioning (SCIM v2, VAPID for web push, DMARCbis/DKIM2 already landed). The pace of RFC implementation is unusually aggressive for an open-source project; the combination of JMAP, CalDAV, IMAP UIDONLY/UIDBATCHES, and SCIM v2 positions it as a viable self-hosted alternative for organizations that need standards compliance without vendor lock-in.
◆ Prediction
WebAuthn/passkey-based authentication and improved multi-tenant administration tooling are the most likely next capability additions, given the current trajectory toward enterprise identity management.
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.
Signal Desktop
Signal adds granular notification controls: badge content, muted threads, restore defaults
Zoho Cliq
Zoho Cliq 7.0 bets on AI conversation summaries and Neat hardware to close the gap with enterprise messaging platforms
Krisp
Krisp adds deepfake detection and expands Voice Translation as its Call Center AI platform deepens enterprise compliance tools.
Netcore Cloud
Netcore's recent entries are blog content, not product releases — the signal is a BFSI and ecommerce vertical sales push.
Canary Mail
Canary Mail ships AI chat history while sustaining a cross-platform bug fix cadence.
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.
- 7d agoProton BridgeSecurity patches and RFC3501 IMAP compliance fixes
- 9d agoStalwartv0.16.21
- 17d agoStalwartv0.16.20 ⚡
- 22d agoStalwartv0.16.19
- 29d agoStalwartv0.16.18
- 1mo agoProton BridgemacOS 27 crash fix, vulnerability patches, Go 1.26.4 toolchain
- 1mo agoStalwartv0.16.17
- 1mo agoStalwartv0.16.16
- 3mo agoProton BridgeVulnerability patches, toolchain update, legacy code removal
- 4mo agoProton BridgeGo base image update to Debian Bullseye
- 4mo agoProton BridgeRestore previous IMAP unlabel endpoint behind feature flag
- 5mo agoProton BridgeIMAP connection limiting and message decryption buffer pooling
Frequently asked questions
What is the difference between Proton Bridge and Stalwart?
They serve adjacent needs but don't currently overlap on shipped themes. Stalwart is currently shipping more aggressively (velocity 6.3 vs 5.0), with 1 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 6.3 vs 5.0), with 1 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.