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Comparison · Comms
Slack vs Stalwart
A side-by-side editorial comparison of Slack and Stalwart — release velocity, themes, recent moves, and the top alternatives to consider.
Slack vs Stalwart: at a glance
What is Slack?
Slack is shipping its developer platform to coding agents, not only to developers.
The developer changelog runs two tracks at once. One is a routine modernization wave across the client libraries: Bolt for JS reached v5, the Node SDK packages took coordinated major versions, and the CLI shipped twice in ten days. The other is newer and smaller in volume but larger in intent, aimed at AI tooling rather than at people writing apps by hand.
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.
Slack vs Stalwart: editorial side-by-side
Slack
6.3COMMSCOLLAB
Slack is shipping its developer platform to coding agents, not only to developers.
◆ Current state
The developer changelog runs two tracks at once. One is a routine modernization wave across the client libraries: Bolt for JS reached v5, the Node SDK packages took coordinated major versions, and the CLI shipped twice in ten days. The other is newer and smaller in volume but larger in intent, aimed at AI tooling rather than at people writing apps by hand.
◆ Where it's heading
The MCP and Skills plugin is the clearest signal of where this is going: Slack is packaging its own platform knowledge for consumption by coding agents, and naming Claude Code and Cursor as the first targets rather than shipping a generic endpoint. Meanwhile the SDK work is clearing debt that would get in the way, dropping axios for native Fetch, removing the deprecated Workflow Steps from Apps feature, and raising the Node floor to 20. Modern runtime, fewer legacy surfaces, then agent access on top.
◆ Prediction
The plugin ships for two named agent clients today, so the obvious next step is broadening that list or folding the skills into the CLI itself. The entries do not indicate whether Slack intends the MCP server to reach runtime app behaviour or stay a build-time developer aid.
Stalwart
5.0COMMS
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 Slack 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 Slack or Stalwart.
Proton Bridge
Proton Bridge spends its first release in ten weeks on crashes, memory bounds and dead code
Mux
Every manual control Mux ships now arrives with a Robots workflow that does it for you
Netcore Cloud
Netcore's feed remains a demand-generation channel; ten entries, zero product releases.
mailcow
mailcow's release notes are almost entirely upstream security currency.
Openfire
Openfire keeps its XMPP server current without changing what it is.
See all Slack alternatives → · See all Stalwart alternatives →
Recent activity from Slack and Stalwart
Latest ship moves from both products, interleaved chronologically. ⚡ = editorial spark.
- 1d agoStalwartResource limits arrive for inbound reports and RocksDB caches
- 8d agoStalwartIMAP gains UIDONLY, UIDBATCHES and message-limit extensions
- 16d agoStalwartJMAP delivery push arrives; strict relays stop rejecting calendar mail
- 19d agoSlackAnnouncing the Slack MCP and Skills Plugin ⚡
- 20d agoSlackRelease: Slack CLI v4.6.0
- 23d agoStalwartFix-only release: JMAP semantics and a credential escalation
- 29d agoSlackRelease: Slack CLI v4.5.0
- 29d agoStalwartVAPID lands for JMAP Web Push
- 1mo agoSlackRelease: Bolt for JS v5
- 1mo agoSlackRelease: Multiple Node Slack SDK package updates
- 1mo agoSlackDesktop notifications now pull text from blocks first
- 1mo agoStalwartFreeBSD support, plus OAuth scopes for IMAP, SMTP and Sieve
Frequently asked questions
What is the difference between Slack and Stalwart?
They serve adjacent needs but don't currently overlap on shipped themes. Slack 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 Slack better than Stalwart?
Sparkpulse doesn't pick a winner — we score release velocity, not feature parity. Slack 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 Slack?
Top Slack alternatives in Comms are ranked by recent ship velocity. Browse the "Slack alternatives" section above for the current picks, or visit /alternatives/slack 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.