outbound email issue - externaldomain@internaldomain address

We are having an issue with our GroupWise system, where it appears, for unknown reasons, internet messages coming in are generating an immediate response, back to a "malformed" address.

GroupWise 2012 SP2
SLE-10-x86_64-SP2 + "online updates"


diagnostic logs shows this:

11:37:54 F056 DMN: MSG 18348156 Accepted connection: [10.100.250.56] (newspam.bcsc.k12.in.us)
11:37:54 F056 DMN: MSG 18348156 Receiving file: /media/nss/DOMAIN/BARTH/wpgate/gwia/receive/21f38325.352
11:37:54 F056 DMN: MSG 18348156 Recipient unknown: gmail.com@bcsc.k12.in.us
11:37:54 F056 DMN: MSG 18348156 Recipient unknown: gmail.com@bcsc.k12.in.us
11:37:54 F056 DMN: MSG 18348156 SMTP session ended: [10.100.250.56] (newspam.bcsc.k12.in.us)



where you see the external domain @ our internal domain...
I can't count the number of different domains that are showing up, so I don't think it is an issue with a single account internally, or domain externally...

I am clueless as to how to troubleshoot this..

Looking at my GWIA, on the ESMTP settings page, Enable Delivery Status Notification (DSN) is unchecked.

Any thoughts would be appreciated.