Limiting sending emails

Hi All

Recently I was hit by a spammer, they paid for a new domain and hosting and of course we st up the plan only to find 24 hours later they were sending spam (Nigerian scam type emails)

Anyway I have implemented better limits to limit the potential problem with this type of thing but it got me thinking.

Within cPanel as far as I am aware at the moment you can only set a blanket limit on how many emails can be sent from certain domains.

Is it possible or even feasible to have an incremental limit on the domains for example a newly created account can say only send 50 emails an hour but 1 set up several months ago (and presumably trusted) can send say 500 emails an hour?