Well as some of you know I run a hosting company. Well someone ordered hosting from a stolen paypal account and then used that hosting they ordered to run a mail spammer. Then when I found out that the paypal was stolen I suspended the hosting but I was to late, the person already sent 1000's of emails.

Then... my server provider fines me $25 for the spam complaints they got. I have to pay or they would suspend my server. So I paid.

And I can't make the client pay for it because the paypal was stolen so I can't file a dispute and get the client to pay for the fine

Well that kind of sucks for me now.

weak...

disable the mail function unless

I can't disable php mail. I am a premium web host. I have limited emails to 80 outgoing per hour to reduce the chances of it happening again on a large scale. I am also planning to not allow people to order from a vps (person ordered from a vps in Amsterdam that I got shutdown because of this).

should really give forum hosting a shot , there's no way they can abuse that.

There are too ways to abuse forum hosting, but I won't go into detail. If abusive people want to abuse hard enough they will find ways.

there's a way to abuse every service, but forums would be easier to enforce as they wouldn't have access to an FTP/backend

Well I would rather not enter the forum hosting business because then I have to buy a script for the forums and etc... It is easier just to do web hosting.