Is $2/mo or $10/year enough to make a viable business and living?

I love, love this idea and how you've done it. But I'd be really sad to see the service take off and you can't support it because the model doesn't work.

I just worry about you charging a flat rate for something that has a variable cost (email). That's assuming you're using a service like Mandrill or SendGrid and not rolling your own.

Anyway, kudos. I love the looks of this and will probably be a paying customer several times over.