Include (encrypted) server passwords in exported settings

[cketti]

Currently server passwords are not included in the exported settings file.

Allow the user to supply a backup password when exporting settings. This password can be used to encrypt the server passwords. When importing settings the backup password needs to be entered to decrypt the saved server passwords.

[hannesa2]

There was already an attempt to do this https://github.com/k9mail/k-9/pull/4700

[openfnord]

I know what I do!

So if the user wants to export passwords, produce a warning and let him. People use encrypted file systems and should know what to do with credentials. Also if a password gets stolen, one can change it at the server. As email is plain text $your_friendly_government_agency has your mail already if you are not using gpg. So the hack value is not that critical to stop users from exporting passwords with settings.

This is not windows, users know what they do.

[openfnord]

I have more than 10 email accounts, entering passwords in about 5 android devices I own is just such a pain.