Rspamd
Rspamd 4.3 fixes SPF evaluation order and rejects weak DKIM keys, with results that change.
Comparison · Comms
Mailu vs Slack
A side-by-side editorial comparison of Mailu and Slack — release velocity, themes, recent moves, and the top alternatives to consider.
Mailu vs Slack: at a glance
What is Mailu?
Mailu's October: patched PHP for webmail, and a resolver that reports DNS failures
Mailu's 2024.06 branch ships pinned releases, each tied to a single issue. October brought resolver fixes for the DNSSEC KSK rollover and SERVFAIL healthchecks, Roundcube 1.6.20, then PHP2Shell CVE mitigations in webmail followed by the patched PHP runtime. 2024.06.68 on 8 November carries the same PHP2Shell mitigation note again.
What is Slack?
Slack now hosts any A2A agent without Slack-specific code.
Slack's developer channel is almost all agent plumbing. On 10 November Slack became an A2A (Agent2Agent) client: a team hosts its own agent, publishes an Agent Card, and Slack calls it when people talk to it, with no request URL, event handling or Slack-specific logic. This follows Slackbot skills managed through Web API methods, a Slack CLI that points coding agents to the Slack MCP server, and a new requirement that Work Objects embeds allow the slack-mcps.com frame ancestor.
Mailu vs Slack: editorial side-by-side
Mailu
5.0COMMS
Mailu's October: patched PHP for webmail, and a resolver that reports DNS failures
◆ Current state
Mailu's 2024.06 branch ships pinned releases, each tied to a single issue. October brought resolver fixes for the DNSSEC KSK rollover and SERVFAIL healthchecks, Roundcube 1.6.20, then PHP2Shell CVE mitigations in webmail followed by the patched PHP runtime. 2024.06.68 on 8 November carries the same PHP2Shell mitigation note again.
◆ Where it's heading
The project remains in one-fix-per-release maintenance on the 2024.06 line, with upstream webmail and PHP security driving much of the cadence. Nothing in the entries points to a new main release.
◆ Prediction
The next releases will most likely follow upstream Roundcube or PHP security fixes, as three of the last six did.
Slack
6.3COMMSCOLLAB
Slack now hosts any A2A agent without Slack-specific code.
◆ Current state
Slack's developer channel is almost all agent plumbing. On 10 November Slack became an A2A (Agent2Agent) client: a team hosts its own agent, publishes an Agent Card, and Slack calls it when people talk to it, with no request URL, event handling or Slack-specific logic. This follows Slackbot skills managed through Web API methods, a Slack CLI that points coding agents to the Slack MCP server, and a new requirement that Work Objects embeds allow the slack-mcps.com frame ancestor.
◆ Where it's heading
Slack is lowering the cost of putting outside agents in front of its users: first skills as code, then MCP pointers for coding agents, now a standard protocol in place of the Slack app model for agents. The platform is positioning itself as the place where agents built anywhere meet the people who use them.
◆ Prediction
Expect more A2A follow-ups, such as agents appearing in Slackbot or skills surfaces and richer Agent Card features, given how fast the agent releases have stacked up since October.
Alternatives to Mailu and Slack
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 Mailu or Slack.
Twilio
Twilio's voice AI stops cutting callers off mid-sentence, using its own turn-taking model.
Salesmsg
Salesmsg adds call-back requests and a one-click Emergency Stop for all outbound texts.
Element
Element 1.12.35 follows the call picture-in-picture release with one desktop storage fix.
Krisp
Krisp moves call transcripts and live captions to cloud transcription in KrispCX 2.84.4.
Misskey
Misskey 2026.11 ships: a leaner start script, and Node.js 22 no longer boots.
Recent activity from Mailu and Slack
Latest ship moves from both products, interleaved chronologically. ⚡ = editorial spark.
- 4d agoSlackBring your A2A agents to Slack ⚡
- 5d agoMailu2024.06.68 re-ships the PHP2Shell webmail mitigation
- 8d agoSlackWork Objects embeds require the slack-mcps.com frame ancestor
- 10d agoSlackSlack CLI 4.13 tells coding agents about Slack MCP and Skills
- 10d agoSlackSlack Skills Plugin installs in Claude Code from its own marketplace
- 12d agoSlackUpdated low-usage submission criteria for Slack Marketplace apps
- 15d agoSlackSlack CLI 4.12.0, the fourth CLI release in October
- 22d agoMailuMailu ships patched PHP for PHP2Shell CVEs
- 22d agoMailuMailu mitigates PHP2Shell webmail CVEs
- 24d agoMailuMailu 2024.06.65: Roundcube 1.6.20 update
- 1mo agoMailu2024.06.64 re-ships the resolver healthcheck fix
- 1mo agoMailu2024.06.63 makes the resolver healthcheck catch SERVFAIL
Frequently asked questions
What is the difference between Mailu and Slack?
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 Mailu better than Slack?
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 Mailu?
Top Mailu alternatives in Comms are ranked by recent ship velocity. Browse the "Mailu alternatives" section above for the current picks, or visit /alternatives/mailu for the full list with editorial commentary on each.
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.