I have recently installed Exchange 2007 into an existing Exchange 2003 environment. Both applications are being supported on a native Windows Server 2008 environment. The Exchange environment is configured as the following:
two front-end servers, 2 CAS servers, and 4 mailbox servers.
A small group of IT staff has been moved over to one 2k7 mailbox. These accounts are having an intermittent issue with sending emails to distribution lists. Sometimes the messages are sent to the group, and other times the users in the group do not receive the message. The message log does not show any messages being sent when they don't receive them.
I have run a clean profile on their outlook, made sure they deleted the group from contacts, and the NDK file. I also made sure they were using the GAL and not a local contact. The distribution group is set as a global group.
2k7 users never receive NDR's and I don't see any errors on the server. The emails just seem to drop. People in the 2k3 environment are not experiencing this issue.
Does anyone know of why this is happening, and what could be the resolution.