I found after installing ISPConfig on Mandriva and FC5 using the Perfect setup path that on Mandriva my pop3 session from outside start only 30-35 seconds after the request was sent to the server - making mail software go nuts!
The resolve was to change the /etc/xinetd.d/ipop3 and imap files to have
log_on_success += HOST
log_on_failure += HOST
instead of the default values that causes an reverce lookup that in most cases will fail. FC5 uses devcot and doe not have this issue!
The second related problem solved some funny SQL failures that causes ISPSetup to fail while connecting to the real internet adres
In the /etc/hosts file using the standard Perfect setup (actually any setup provide this outcome) you gave this in the /etc/hosts file:
127.0.0.1 host.domain.tld host localhost
it should be
127.0.0.1 host localhost
were x.x.x.x represent your REAL IP adress to the internet
Now the ISPConfig will find the server and complete the install.