Would I pay for this? No.

Who uses auto-fill? Everyone and their grand mother.

I think it would be kind of a strange idea to auto fill name by E-mail. I don't even use my name anywhere in any of my E-mails except for my initials (Good luck getting my name from them).

I can't see why anyone would pay for this as a service... Maybe if it was free, opensource and client-side only you would find somebody who would use this... I can see the interresting aspects of making this and I hope you had a lot of fun and learning doing it.