@morrow without logs this will be hard to track down. can you ask your administrator to open up a support case for this?
A update from Debian GNU/Linux 4.0r3 "Etch" and Ubuntu 8.04 will remove Zarafa, by upgrading libvmime0
Calculating upgrade... Done The following packages will be REMOVED: zarafa zarafa-webaccess The following NEW packages will be installed: libgsasl7 The following packages will be upgraded: libvmime0 1 upgraded, 1 newly installed, 2 to remove and 0 not upgraded. Need to get 944kB of archives. After unpacking 16.2MB disk space will be freed. Do you want to continue [Y/n]?
Since the libvmime API of 0.7 and 0.8 is completely different, we indeed hold the upgrade from Debian Etch back.
However, this is not an issue, since no other package in Debian depends on 0.8. You can set the libvmime0 package on hold with the command
echo libvmime0 hold | dpkg --set-selections