This could also happen when the exchangeserver is failing to contact the domaincontroller (Global Catalog Server). I had big problems with this on service pack 2 for Exchange server. What do the logbooks tell you on the domailcontroller and on the exchangeserver. The second reason could also bee that the exchangeserver is trying every 5 min to update and run the security templates that you have. If it fails it tries again. This killing the server and you could get this message in Outlook also. Reason no. 3 could also bee a delay in the DNS. Are you running in native mode or not on Exchange and on the domain? Try to implement wins if you don?t use it. If this helps the network, then you have some problem with DNS questions. Reason no. 4 is if your raidcontroller is trying to run a sync on the disks because some disk have bad blocks and is not able to fix the problem. The first thing I would do is just to look at the Exchange server for 30 min. You could see diskactivity above normal rate very easy. Then it could be no.1-4. If you are running service pack 3 on the exchange server then there is a patch to this servicepack. Without this patch the exchange server will take to much effort to do internal matters. Best regards Magnus Hellström IS-Manager Neoventa Medical AB Magnus.hellstrom@xxxxxxxxxxx mailadmin@xxxxxxxxxxxx