Retracing Sender's SMTP IP Address using MS Exchange 5.5

Dear Folks, We receive an e-mail that we want to reply back, but the sender's SMTP is NOT registered in DNS. Let's say the sender is who@xyz.com. Let's assume xyz.com is being resolve with its ISP DNS 150.150.150.1. But there is no MX for xyz.com in this DNS. Our e-mail is MS Exchange 5.5. Can we trace the sender's SMTP IP address? Is there better way than to peel off the original header packet to see the sender IP? Thanks, Audie Onibala ____________________________________________________________________ Get free email and a permanent address at http://www.netaddress.com/?N=1