Problems with microsoft mail addresses

Microsoft has decided that My machine is for some reason dangerous, and
refuses to accept mail for any microsoft type address (eg msn.com,
hotmail.com,...). I certainly have not engaged in spamming anyone, or
any of the other "bad things" and neither has my machine. They of course
refuse to tell me why they are blackballing me. 

Since we have friends who use microsoft mail addresses, this makes it
almost impossible to get mail to them, and we cannot ask them all to
change to some more reasonable mail address. 

Is there some way of rewriting the headers so that the mail appears to
come from another machine, eg, the one pointed to by our return address,
instead of the machine the mail is actuall coming from. 
Eg, the return address is phy.univer.ca, but my machine is
theory.phy.univer.ca, and thus the source (Received: header) is the
latter. Is there someway I can get postfix to rewrite the header so that so it appears
to come from phy.univer.ca?