The future of communications is now. Traditional email has problems ranging from reliability to just too much spam. LiteNote (RSL), a cryptocurrency with support for built in email-like messaging, solves all these problems.
Using our new model, spam can be stopped just by ignoring it. Sending a message costs a small amount of LiteNote, and you get LiteNote whenever you receive a message. If you do not reply to spammers, they will eventually run out of LiteNote and be unable to send more spam.
E-mail is standard and free. Paid non standard service as you propose has no chances at all. Of course it could work in a small closed community, but even there everyone could be free of spam by simply avoiding disclosing e-mail to outside of the group.