I have a new 2007 Exchange server migrating from Exchange 2003The Outlook 2007 clients don't appear to have a problem. However the Outlook 2003 clients get an error "An object can't be found"This only happens when I turn off the 2003 Store. SO I am assuming that there is something still left in the 2003 store that the client is looking for. The same user mailbox (mine) works on OL 2007 but hangs up with this error on OL 2003.I am guessing it could be the Newsgroup public folder, but thats just a guess. We haven't used NNTP for a long time so I removed it completely, but the Newsgroup folder is still there on the 2003 side.I still havent found the contents of the public folders on the Exchange 2007 side, so not sure if its really there or not.I tried the get-mailpublicfolder to see what that does, but it gave a handful of errors relating to the 2003 DB saying it is corrupted.Why in the heck do we need command line tools for major operations like this is beyond me, but anyway that doesnt finx the problemI am guessing that if I remove the Newsgroup folder then that might be the missing object the client is looking for. It wont let me remove it however... I assume there is a command line tool in Exchange 2003 to so this? Any ideas!?? thanks for the help!!

It's look like a OAB issue.In your exchange 2007 does have any public folder store? Outlook 2003 client still need public folder to store OAB information,please make sure your default OAB(in Exchange 2007) has enable support outlook 2003 client. Please see How to View and Modify Offline Address Book Settings

Turns out all clients get this error, the 2007 client its not as obvious that there is an error.The OAB is all set for everyone