I would suggest the kolab server.
The Pro's:
Opensource
KDE Client available
Full KDE integration under development (Kontact)
supported by Aethera
Outlook Connectors are available
(currently working ones are from companies like Bynari etc.)
(some projects are working on opensource MAPI connectors)
A Webclient based on Horde is under development (probably that will be
integrated into horde mainstream)
The Con's:
Currently only OpenPKG rpm's are available (except Mandrake)
It requires an LDAP Server, so it's probably not a solution for little
sites
Sincerly,
Klaus Steinberger
--
Klaus Steinberger Maier-Leibnitz Labor
Phone: (+49 89)289 14287 Am Coulombwall 6, D-85748 Garching, Germany
FAX: (+49 89)289 14280 EMail: Klaus.Steinberger(a)Physik.Uni-Muenchen.DE
URL:
http://www.physik.uni-muenchen.de/~k2/
In a world without Walls and Fences, who needs Windows and Gates