Hello. I was wondering if someone could give me some insight on the problem i'm having. I have a user that is receiving these undeliverable email messages in their inbox. The thing is the user is not sending these emails. There is no indication in their sent items folder that the messages are being sent from their account. The environment is a SBS 2003 Server with Exchange 2003 and client is xp os with outlook 2003. I'm attaching the header and message of one of these emails. I'm thinking these are just spam emails trying to look like undeliverables but I'd rather be sure and not end up on someones blacklist. Here's the things I've tried already. Scanned the user's computer for viruses, nothing came up. Changed user's password and detected and repaired Outlook. And they are still getting them.