After applying hotfix 1 for Plesk 9.2.3, we started experiencing strange problems with webmail, in our case atmail, but it may apply to horde as well, on the server.
A typical example of an error would be:
Unable to get options for atmail webmail
Looking at the files installed by the hotfix, you will notice that the hotfix installs a new copy of:
/usr/local/psa/admin/sbin/webmailmng
which is why the problem starts.
There is a BUG in the newer /usr/local/psa/admin/sbin/webmailmng
Instead of trying to access the config files in
/etc/psa/webmail/atmail/atmail.conf
the new version now looks for a config file in
/etc/psa-webmail/atmail/atmail.conf
My quick workaround is to simply, make /etc/psa-webmail/atmail/ a symbolic link to /etc/psa/webmail/atmail/ which seems to temporarily solve the problem.
The permanent fix is apparently to upgrade to Plesk 9.3.0, which was available at the time of writing.