Email billing has been one of Billtrust's more popular B2B offerings. However, it is a daily battle to manage the delivery of email. There's no way to guarantee to delivery, there's no way to know for sure if someone received an email, there's no way to know for sure if someone opened an email, and there doesn't seem to be any solution on the horizon.
Obviously the problem is spammers and the great lengths that everybody goes through to block unsolicited email. ISPs attempt to block spam, corporations attempt to block spam, all email clients worth their salt have spam filtering built in. The net of all of this spam filtering is that a large percentage of spam is blocked . However, a small percentage of emails that should get through, invariably don't.
So I know it's not a revolutionary concept but can someone please invent an email system that is fee based? Any fee, no matter how small, would be a huge deterrent to spammers. Businesses that send opt-in email want it. People who receive email want it. ISPs would embrace it. The only ones who wouldn't want it are the spammers and the companies that sell spam protection.