I've been experimenting a bit with ALIAS domains.
I noticed that you can add an ALIAS domain and of course it has the same web directory. But it also allows you to setup email accounts under the ALIAS domain but if you try to RECEIVE emails it gets denied by the mail server.
Is this intentional? a bug?
You can SEND FROM but cannot RECEIVE FROM the email.
If the domain is re-added as an ADDON domain then it will be fixed.
