Wrestled with courier webadmin for a bit tonight. The apache2 server I was trying to install it on had a VirtualScriptAlias setup for trac fastcgi, and I couldn't get courier webadmin to work without removing it.
Courierwebadmin is different than most web apps I've used before. There is a binary elf interface to to perl scripts and html templates on the back end.
Once I got it to work, I realized I didn't really need it. It might be helpful for setting up esmtp stuff, but I use postfix for that. Speaking of which I just started a new project Chimailmadmin. Its inspired by the original postfixadmin and uses Nexista as the framework.