Kontact - KOrganizer - KOrganizer is the calendar and scheduling component of Kontact, the integrated personal information...
Zimbra - Zimbra is trusted by over 500 million users to increase productivity with a complete set of collaboration tools while maintaining total control over security and privacy.
hMail Server - hMailServer is a free e-mail server for Microsoft Windows.
Roundcube - Web-based IMAP email client
Microsoft Outlook - Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.
Microsoft Exchange Server - Microsoft Exchange Server is a messaging and collaborative software product developed by Microsoft.