Hi,
I am not sure which version of Exchange you're running, but can you specify the exact error you're getting?
I've put in a couple of links just in case 1 of them has the details you're looking for:
http://seer.entsupport.symantec.com/docs/289276.htm
http://seer.entsupport.symantec.com/docs/269274.htm
http://seer.entsupport.symantec.com/docs/325619.htm