Over this past weekend I ran into an issue with Exchange 2010 Service Pack 3. Even though my Exchange server’s clock was sync’d with my Domain Controller the Exchange server was unable to start the Exchange IS service, and instead was logging the error:
Event 5003: Unable to initialize the Information Store service because the clocks on the client and server are skewed. This may be caused by a time change either on the client or on the server, and may require a restart of that computer. Verify that your domain is correctly configured and is currently online.
After a few reboots, and verification that the windows clocks were actually in sync, I thought to check that the clock in the BIOS was properly configured. Since these machines are VMs on VMWare ESXi, I logged into vCenter and checked my ESXi host. Sure enough one of the three hosts was not configured to use an NTP server, and it’s local clock was off. I fixed that setting and rebooted the exchange server one more time, the server was then able to start the Information store service.