Kolab Community
Kolab Groupware is a secure, scalable, reliable, flexible, full-featured collaboration suite.
20 Alternatives To Kolab Community
Citadel
Is a collaboration suite (messaging and groupware).
Lightning Calendar
Organize your life — it’s about time!
Mail-in-a-box
Mail-in-a-Box provides webmail and an IMAP/SMTP server for use with mobile devices and desktop mail software and also includes contacts and calendar synchronization.
Microsoft Exchange Server
Microsoft Exchange Server is a messaging and collaborative software product developed by Microsoft.
Proxmox Mail Gateway
Protect mail server against spam, viruses and malware with Proxmox Mail Gateway security for businesses, government, education and non-profit organizations.
Rainlendar
Rainlendar - Customizable desktop calendar
Simple Calendar
A simple calendar with events (optional recurring and reminders), week numbers and a customizable…
Zimbra Collaboration Suite
Zimbra Collaboration is an open, secure collaboration tool for email, calendaring, tasks and more.
mailcow dockerized
An open source mailserver suite.