Postfix Domain/Hostname configuration
After ISPconfig setup the main.cf of Postfix looks like: mynetworks = 127.0.0.0/8 [::1]/128 mydomain = xxx.de myhostname = xxx.de mydestination = xxx.de, localhost, localhost.localdomain
But it should be: mynetworks = 127.0.0.0/8 [::1]/128 mydomain = xxx.de myhostname = mx.xxx.de mydestination = $myhostname, localhost, localhost.$mydomain
Otherwise Postfix bounces the mails and give additional warning: warning: do not list domain xxx.de in BOTH mydestination and virtual_mailbox_domains