Once you connect to a service, you are presented with a dialog with three area:
You enter a string in that field and press the "Send" button. The line is sent to the service.
For each button, you set the button label and the string which will be sent. The buttons configuration is preserved by service.
This module is an experiment. I suggest you give it a try. Point it to your SMTP server, and send the "help" command. Then try to send me an email from there. You might guess after that what the S in SMTP stand for :-)
Or test your email vdomains with it. Comments and suggestions welcome.