Arguably the one thing missing from Gmail right now is the ability to pick up the phone and speak to someone when something isn't working.

If you can offer that level of support at the same time, I can't see any reason for a company not to give you money.

Oh, and don't be discouraged by the people saying "no, never!" You can use third parties for handling spam, and it'll be easy enough to get mail onto peoples' phones via IMAP or Exchange. The thing to remember is that plenty of techies will say "no" because they see email as a free service. Regular consumers - and companies in particular - will be much more open to giving you money.