Mail app - automatic provisioning / connecting to email imap account

hi, i have an existing dovecot/postfix/roundcube email server and it works like a charm. so i use for nextcloud the application external_users that allows IMAP authentication. When an existing imap-user logs in to nextcloud.mydomain.tld with his IMAP credentials, the nextcloud account is created, that works.

Now i want to auto-connect the nextcloud account with the email functionality. because the users have 0 idea about IT, they should not configure anything. They should simply login with their imap credentials and be able to read the emails in nextcloud. but it seems like this is not possible?

When i configure nextcloud mail app that this thing does that auto-connect, It is asking for a master password. i dont want a master password. The user already has a password in a database, sha512 crypted with a salt. Is there any way to allow an existing (IMAP) user to connect his account with the email account without providing anything again, after logging in to nextcloud?

I found Mail Provisioning with UserExternal\IMAP but there is no masterpassword at all in the screenshot. Maybe thats a newer feature? Even when the checkbox is deactivated, it still asks for a master password.

created master password is requested even if checkbox is unselected · Issue #9191 · nextcloud/mail · GitHub
looks like a bug