OK, it is clear that email for all the virtual domains rumble in on the 
same IP and Port so it is the pop3 handshake "USER" transmission that 
has to be given the task.  I understand that.  Don't like it, but I do 
understand.  Turns out Eudora OSE aka Thunderbird seems to automatically 
pack on the domain to the user ID. Outlook is a whole different animal.

We will just have to wade through each of our clients and advise them 
what has to be changed.

If any miracle solution occurs to someone, please ship it on over.

On 1/6/2013 12:17 PM, surgemail-support wrote:
> As you've already realized this isn't really fixable.  With virtual 
> domains that don't have an ip the server simply isn't told the 
> connecting domain, so it can't figure it out and requires that the 
> user specify it.
> ChrisP.