nline
> Is a valid domain REQUIRED for this to work correctly...
No, not for sending (in most usual situations), but your email system needs to be configured correctly and your network needs to allow the sme mail server to connect externally.
> Webmail works, once I turned it on.
I didn't only mean does it work as in open, I meant for you to use it to test your servers ability to send & receive mails.
Can you send email to an external address and receive email from an external address using say the admin webmail account on the sme server.
If webmail cannot send (and receive) then something is wrong with your general setup.