Im having a problem with the Offline Address Book in my company. We are in the process of migrating users from Exchange 2003 to 2010 but Im not sure if thats the cause. Some users simply do not show up in the Offline Address book when Outlook is in Cached Mode but you can find the in the OWA Address Book. Strangely though, if I look at the udetails.oab file on local workstation those users are there and I cannot find any attributes in AD or in Exchange that are different for a user that does not appear in the Offline Address Book compared to a user that works. To add to the confusion, those problematic users include users that have been migrated to Exchange 2010 and users that are still on the Exchange 2003 servers. They also come from different OU´s and in short do not have anything obvious in common. I estimate that this is the case for perhaps 5% of my users
So the question basically is why does Outlook in Cached Mode not resolve all items from the Offline Address book, even if that item can be found in the local downloaded Offline Address Book; udetails.oab ?