Rewriting the from address

[Eric]

hi,
i am planning to use my qmail server as a tempory email proxy.
i am after a way that when a users send a email to my internal email server
(email.nyandashs.qld.edu.au) that it will send it on as if it came from
mail.nyandashs.qld.edu.au

as my email server (email.nyandashs.qld.edu.au) doesn't have a live ip i was
wanting to use my live server to collect mail there, then use my local qmail
server to download those msgs to local users.

regards,
eric.