After configuration SMG with DLP for quarantine connect
In the Symantec Messaging Gateway console enter the credentials in the Enforce Server Access tab of the Symantec Data Loss Prevention Setup in the following way:
Enter the FQDN in UPPERCASE letters in the Registered Enforce administration console host or IP address box
This should match what you have speficied in your krb5.ini file for AD authentication.
In the Credentials section enter the User name in the format of username:domain where a colon ':' is used as the separator.