SOGo
Groupware server for calendars, contacts, and email integration.
Why it is included
Groupware server for calendars, contacts, and email integration.
Best for
Organizations wanting webmail/caldav alongside chat stacks.
Strengths
- Open source
- High community visibility
Limitations
- Verify license and support model for your use case
Good alternatives
Related tools
Communication & Collaboration
Delta Chat
Messenger using email as transport—chat over your existing IMAP/SMTP accounts.
Communication & Collaboration
Element (Matrix)
Matrix client for federated, E2EE-capable real-time communication.
Communication & Collaboration
Signal
E2EE messenger with conservative security posture and broad adoption.
Communication & Collaboration
Mattermost
Team messaging platform with strong self-hosted enterprise adoption.
Communication & Collaboration
Rocket.Chat
Team chat platform with channels, threads, video, and broad integration marketplace.
Communication & Collaboration
Zulip
Thread-first team chat combining email-like topics with real-time messaging.