Outgoing Postmaster Address – Question

Hi, I've got mail coming in through a separate scanner relay box being delivered to my OS X Server (10.2) which is running Apple's mail server software. However, when an e-mail addressed to an non-existent account comes in, the OS X server, of course, will respond with a "Local account not found message". However, it comes out as: [quote:a5cbb02da0] From: "Postmaster" <Postmaster@192.168.2.200> Date: December 8, 2003 4:57:09 AM JST To: <yf9fnpx@verizon.net> Subject: Non-Delivery Report[/quote:a5cbb02da0] Any reason it's coming from an IP address and not a domain? Aside from this, all other DNS-related issues are non-existent and I'm wondering if this is a hard-coded entry somewhere that can be changed. Thanks.