how to add domain name to email address (that is different from hostname)

[Globe Trotter]

Hi, 

I am wondering how it is possible automagically add a given domain name to an email address that is not in my address book.

Specifically, if I type joe and joe is in my addressbook (or is not a complete email address) as my recipient, I get:

joe at hostname

what I want to happen is for joe to automagically expand to joe at yahoo.com (say).


This should be possible, but how do I do this?

TIA!