What to expect from the Unfiltered Recipients List once it's enabled the the mail security console (check the box: Bypass spam detection for messages sent to the following)
If a spam message comes through and there is more than one recipient, both recipients need to be on the unfiltered list in order for the message to pass. If only one of the recipients is on the unfiltered list and the other one is not, then the message will be blocked for both recipients. The reason is that when the message comes in, Symantec Mail Security sees only one message in which the recipients field doesn't fully match the condition of the rule (one recipient does needs spam detection) and so it has to block the message. There is no way to allow it for one recipient and not the other.