My environment is Exchange 2007 sp2 and Outlook 2003. Recently I have been getting a lot a calls from users that are receiving DSN's for messages that they did not receive. For instance my user calls saying that they received a notification from our firewall that a message sent to a particular users has not been delivered but a second attempt will be made. When I check the firewall I find that the message is a read receipt. The users tell me that they have not communicated with this particular recipient either not recent or not at all. Any ideas?

My guess is that this is caused by responses to spam messages with forged headers. Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."

Likley NDR backscatter as Ed mentioned. http://spamlinks.net/prevent-secure-backscatter.htm James Chong (MVP) MCITP | EA | EMA; MCSE | M+, S+ Security+, Project+, ITIL msexchangetips.blogspot.comJames Chong (MVP) MCITP | EA | EMA; MCSE | M+, S+ Security+, Project+, ITIL msexchangetips.blogspot.com