As default, the quota warning message goes to administrator. Is it possible to send the message directly to the user affected by the quota limitation?
Which quota message? The one that is sent at 03:15h and 15:15h? I don't think it's a good idea to send it to a user because then he knows who else is over quota, etc. The mail contains quota notifications for all users and groups.
Yes, the one sent 15:15 and 03:15. The message have to be edited, as though it should only contain information about the specific user, not other users.
Is the quota script a part of ISPConfig or quota? And if it is a part of ISPConfig, where is it located?