[Mailman-Users] How to make different versions of an email address look equivalent?

[Marina Markus]

Hello,
 
I am looking for a solution of the following problem. Email users at our
main email server can use two different versions of an email address - one
with the name of the server and one without:
 
user at bgu.ac.il and user at bgumail.bgu.ac.il
 
Is there any easy way to inform Mailmain that these two addresses are in
fact the same (sort of sender address aliasing) ?
Otherwise, a user who is subscribed with the long version of address, and
sends mail with the short version in "From", will have his message rejected
like one from a non-member etc. 
 
Thank you in advance for any idea,
 
Marina Markus
Ben-Gurion University Computer Center
=============================
mary at bgu.ac.il