Comment Re:NEVER trust and AC (Score 1) 279
I somewhat the opposite of you - I run a system that takes requests from users, and generates a shipping label for them. It is emailed to them at the address they provide. And, if that mail bounces because they're using a whitelist, or something like your "visit this URL and fill out a form so I can know who you are" system (like Earthlink), sorry. You paid for your label and refused to accept it, it's not something we really care about.
All of our systems use SPF to validate as a legitimate sender. If that isn't good enough, tough. Have a nice life.