I've got it working, but I had to configure some conf-file manually (some google searching helped me). Configuring email only in webadmin does not work (for me).
The right place to start is /etc/postfix.
You should check main.cf (relayhost, tls-settings, certificates,network protocol) sasl_passwd and transport.
After configuring sasl_passw and transport you have to do a postmap (one for sasl_passwd and one for transport.
At last postfix restart (not reload) and things are working.
Now you can use general info plugin to send emails.
If it is not working check /var/log/mail.log.
Cheers,
bernd