With https://mail.example.com/postfixadmin/setup.php I checked my mail server and all tests were OK. I generated a hash for the password and included it into the /var/www/postfixadmin/config.inc.php file. The https://example.com/postfixadmin/login.php generates an error "Your email address or password are not correct." For example.com I use my IP address. Any suggestions are appreciated.