I can't seem to send or receive mail

Yes I think at this point a quick re-install of your entire system and make sure you follow these spot on install guides everything should be fine.... fingers crossed.... I found that only after a few re-installs did I start to understand everything and get it all working.

 

For a system that is as big and interacts with as many components as ISPConfig does, IMHO, doing a few installs just for the heck of it is a good idea.
________
Subaru ef engine