This makes sense, It'd be pretty easy for them to sign up for a domain, and then use the trial credits for sending spam/telemarketing from your SMTP servers. Th

This makes sense, It'd be pretty easy for them to sign up for a domain, and then use the trial credits for sending spam/telemarketing from your SMTP servers. Though how do you deal with people using subdomains? Do you block the whole domain? How does that work for eTLDs like co.uk