The password-file is created after first opening the admin UI!
Be sure to immediately change the default password!
Open Snappy's admin UI `https://__DOMAIN____PATH__/?admin` to configure your mail server settings. Login with user "admin" and password from the file `__INSTALL_DIR__/data/_data_/_default_/admin_password.txt`.
In particular, to be able to send emails, you need to go to Snappy's admin UI > Domains > __DOMAIN__ > SMTP > Check "Use authentication"