We have an Exchange 2010 Enterprise Edition Server running on Windows Server 2008 R2 Enterprise Edition. Its a single Exchange server setup, we have a separate AD server. Whenever we install Symantec Mail Security for Microsoft Exchange 6.5, within a few hours to a few days, we stop recieving email. When we unistall the SMSMSE, mail flow starts again. Because its our production server, we have not had a chance to spend too much time trying to figure out why mail flow is getting affected by SMSMSE.