Rspamd
Rspamd 4.3 fixes SPF evaluation order and rejects weak DKIM keys, with results that change.
Comparison · Comms
Maddy vs Slack
A side-by-side editorial comparison of Maddy and Slack — release velocity, themes, recent moves, and the top alternatives to consider.
Maddy vs Slack: at a glance
What is Maddy?
maddy's back-to-back security releases close DMARC bypasses and IMAP storage bugs.
maddy is an all-in-one Go mail server for SMTP and IMAP. Its last two releases are security fixes: 0.9.6 in October required explicit trust for PROXY headers and closed an auth misconfiguration, and 0.9.7 fixes two DMARC verification bypasses that let attackers spoof domains with p=reject, plus long-standing IMAP storage bugs. Malformed MIME messages are now stored as a single part instead of being lost.
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.
Maddy vs Slack: editorial side-by-side
Maddy
2.5COMMS
maddy's back-to-back security releases close DMARC bypasses and IMAP storage bugs.
◆ Current state
maddy is an all-in-one Go mail server for SMTP and IMAP. Its last two releases are security fixes: 0.9.6 in October required explicit trust for PROXY headers and closed an auth misconfiguration, and 0.9.7 fixes two DMARC verification bypasses that let attackers spoof domains with p=reject, plus long-standing IMAP storage bugs. Malformed MIME messages are now stored as a single part instead of being lost.
◆ Where it's heading
Feature work stopped after the 0.9 line in spring; recent releases are driven by reported vulnerabilities. The project is fixing correctness in mail authentication and storage rather than adding capabilities.
◆ Prediction
Further security point releases look more likely than a 0.10.0 feature release, though 0.9.1 flagged libdns provider removals for 0.10.0.
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 Maddy 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 Maddy 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 Maddy and Slack
Latest ship moves from both products, interleaved chronologically. ⚡ = editorial spark.
- 4d agoSlackBring your A2A agents to Slack ⚡
- 8d agoSlackWork Objects embeds require the slack-mcps.com frame ancestor
- 8d agoMaddymaddy 0.9.7 fixes two DMARC bypasses and IMAP storage bugs
- 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
- 1mo agoMaddymaddy 0.9.6 fixes PROXY trust and auth bypass misconfig
- 5mo agoMaddymaddy 0.9.5 fixes nested pipeline logging and systemd reload reporting
- 6mo agoMaddymaddy 0.9.4 removes the maddyctl symlink and implicit run command
- 7mo agoMaddymaddy 0.9.3 patches an LDAP injection flaw in auth.ldap
- 7mo agoMaddymaddy 0.9.2 fixes an rspamd panic on unspecified tls_client
Frequently asked questions
What is the difference between Maddy and Slack?
They serve adjacent needs but don't currently overlap on shipped themes. Slack is currently shipping more aggressively (velocity 6.3 vs 2.5), 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 Maddy 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 2.5), 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 Maddy?
Top Maddy alternatives in Comms are ranked by recent ship velocity. Browse the "Maddy alternatives" section above for the current picks, or visit /alternatives/maddy 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.