Some of our users who use Outlook 2003 have the same problem. Every couple of minutes, they get this message: "Task 'Microsoft Exchange Server' reported error (0x8004010F): The operation failed. An object could not be found." E-mail does come in and go out without any problems, but this error keeps appearing on the screen. What could be wrong? We use Exchange 5.5 on an NT4 server. This answer below I got from searchexchange website. > EXPERT RESPONSE VIEW MEMBER FEEDBACK TO THIS ASK THE EXPERT Q&A. You may want to try changing the mail profile out of cached mode to alleviate the problem. You may also want to try doing a rebuild from Exchange Manager. Go to Recipients -> Offline addresses -> Default offline address list. Right click and then rebuild. The problem is that I have read this answer everywhere at the internet...But I can't find ''Offline addresses'' at my exchange 5.5, neither Offline addresses list...nothing... I have already unchecked the cashing mode box at the user profile and it didn't help. Thanks in advance...