Apache document tree location on Fedora

Last night I was taking a look at the web server configuration that was set up by default when I installed Fedora. The /var/www/html was specified as the document tree. I also noticed that Squirrelmail was set up by default as well in /usr/share/squirrelmail (or something like that). In the httpd.conf file I fail to find a reference to Squirrelmail as an alias. I am wondering how this works. I can connect on the web as http://myserver/webmail (example) and it finds the /usr/share/squirrelmail directory.