We have several different websites. Our main website (www.site.com) is hosted on another box but several other sub domains (site1.site.com, site2.site.com, etc) are hosted on an ispconfig box. We noticed that we were not getting mail sent by forms on the sub domain sites hosted on our ispconfig box. We checked the error log and saw that it was looking for the main domain, and since it is not hosted on that box, it would just give an error and not send. To fix this we removed "site.com" from etc/postfix/local-host-names and then mail was being sent fine. But, every time you interact with the admin panel, it adds "site.com" back into the local-host-names file. Any ideas how to stop this?