I'm thinking about trying something similar to this on top of AWS SES. They make it fairly trivial to accept email and store it to S3. So email forwarding would be straight to S3 backup. But still would need a system to backup these emails to some local storage.

Not sure what's the best way to handle this, I had my gmail account since the early days and it's baked into so many important accounts. It definitely crosses my mind what it'd be really difficult if I were blocked out somehow.