I release an item from quarantine by email. The item shows as gone from the Quarantine. However after a refresh the item shows back up in the Quarantine.
Symantec Mail Security for Microsoft Exchange has an issue in the code that handles release by email on a server with no access to active directory.
This problem is fixed in Symantec Mail Security 6.5.1 for Microsoft Exchange. To download the latest release, read Obtaining an update or an upgrade for a Symantec Corporate product.