Thanks for the note, Chiliberto. It’s true, right now if you want to change your email address in WordPress, you have to stop using PrefPass for that site. The password being autogenerated, however, is just due to the fact that you revert to the normal WordPress behavior.
PrefPass needs some global identifier to know who you are across sites; right now that identifier is email address. We’re planning on allowing users to have multiple email addresses in the future, which would solve this problem. Do you have any thoughts as to how you’d like to see this handled within the plugin? We’d love to hear your ideas or additional feedback.