I use mod_php as an admin at 7 servers for few years. 
The strange thing is when someone from one server sends spam through php mail(). 
Checking apache-logs, checking php files on the server... uff....
The solution for such problems (and this is very popular problem for admins) will be possibility to log every call of the mail() function.
Such log should consist of:
- datetime
- path and file name of the php-caller-script

If this is possible to add such very usefull future?

THX