To confirm if a timing conflict exists follow these steps:
Set the Symantec Mail Security for Microsoft Exchange service to manual.
Restart the server.
Start the Symantec Mail Security for Microsoft Exchange service.
If the service starts successfully then a timing conflict is a likely cause for the problem.
One solution for a timing conflict is to make the Symantec Mail Security for Exchange service dependent upon another service, such as the Microsoft Exchange Information Store service (MSExchangeIS).
WARNING: This information is provided "as-is" and as a courtesy only. In the next steps, you will edit the Windows registry. Back up the registry before you make any changes to it, because incorrect changes to the registry can result in permanent data loss or corrupted files. Modify only the registry keys specified. Because these steps involve a change to Windows settings and not Symantec settings, if you have any questions about the steps please contact Microsoft Technical Support.
The following documents explain how to back up the registry