and set the MAIL settings, if you're planning to use your local email server the default settings will work for you
MAIL_SERVER = env('MAIL_SERVER', 'localhost')
MAIL_PORT = int(env('MAIL_PORT', 25))
If you're using an external account you have to specify the settings, at least
MAIL_USE_TLS, MAIL_USERNAME, MAIL_PASSWORD
Any edit to that file needs Superdesk to be restarted for the changes to take effect
root@superdesk:~# systemctl restart superdesk
If you've installed Superdesk through the automated script, it also installs a test smtp server for you. If you're planning to use a local postfix instead, make sure you disable that