We are having issues with bounced meeting request messages. The recipients have been out of the company for 4 or 5 years. There is no exchange account associated with these users, and the mailboxes are long gone. I have run the /cleanrules switch on offending users getting the NDR's, and I have added and removed delegates. Searching this everyone points to a ghost delegate issue, but anyone sending a meeting request to certain users will get the same NDR, so I am now thinking it has nothing to do with rules or delegates. It is happening on machines with XP and Vista, whether they are running Outlook 2003 or 2007. This seems to me to be coming from the Exchange server or Active Directory, but I can't find it. I have use MDBVU and have not found any hidden delegates or rules, I have the Active Directory CSV files from all of our domain controllers and am not seeing any delegations to users. It can't be from and individual users profile, or delegates, or rules, because it will happen to anyone. Could this be an address book issue?