Can I selectively enable each users SMTP on a CPanel server?

I am so sick of getting whacked for spam abuse via resellers customers that I want to introduce a policy that means ID required etc for any client wanting to use our mail relay.. otherwise they can use their ISP's or other. Incoming is fine. Nobody here right now to answer my question and I'm impatient.

Thanks in anticipation.

Felix if you come up with a solution please let me know as well. I was going to post this exact samething when I ran across your post. Has the ID thing slowed sales down at all?

Ironlung,

I haven't done the ID thing yet .. just considering it.. damn it's hard to keep everyone happy.. I'm hoping it can be done easily, but I'm just a humble salesman so if I get a fix I'll let you know..

Is there a solution for this?

Maybe in Qmail set the limit to only allow a certain amount per hour?? Still does not stop the spam but if the spammer can't send out a million emails they will move on. ???