The function log_into_server uses a wrong password when sending a testmail via email settings.
The password is always "********" independent of previously entered passwords.
However, the password stored in database is correct. When the password is hardcoded into the function it works.

Probably, when clicking the button "send a test email" without entering the SMTP password newly just before, the board interprets the content "********" of the SMTP password field as password.