Open Source Collaboration, providing:

 Integration with your existing Linux mailserver
 Number one MS Exchange replacement
 Integration with your existing Linux mailserver  
 Native mobile phone support
 Outlook "Look & Feel" webaccess
 Outlook compatible (100% MAPI)

Cost-effective:

 Initial investment and upgrades cost less than 50% of MS Exchange
 Effective sharing via multiple clients
 Effective communication by sharing e-mail, calendar and contacts
 Support for IMAP and iCal based clients
 Work wherever you want
 Webaccess compatible with Internet explorer and Firefox
 Remote Outlook synchronization over HTTPS
 Advanced offline mode for laptop users
 Remote synchronization & push-mail of all ActiveSync compatible PDA’s and phones (Windows Mobile, iPhone, Nokia Mail for Exchange) 
 

Technical benefits:

 Freedom to integrate your own Linux MTA like Postfix, Sendmail, or Qmail

 Easy migration: Via migration tools, data can be imported from existing MS Exchange   environments or IMAP based solutions
 Multi-user week calendar in webaccess
 Brick-level backup with single item and single mailbox restore
 Integration with existing LDAP environments, like OpenLDAP, Active Directory, or     eDirectory Open source & open standards
 Source code available under the Affero GPLv3 license
 Open architecture supporting Apache, MySQL, PHP
 Gateways to IMAP, POP3, iCal, Caldav