Exchange 2007 and Delivery Restriction : In Exchange 2007 there was a feature of Delivery Restriction in which an Exchange administrator can setup that a User A cannot Send email to a Distribution Group named “All Users”. Thus this Rule  only allowed for explicitly setting restrictions on distribution lists with the options to "Accept messages from", "Reject messages from" or "Require that all users are authenticated".

With Exchange 2010 and Email Moderation now You can Setup All your users to send email to the Distribution List but have Designated Moderators to Monitor Or Approve/Reject Emails send to those Lists.

Thus the decision is taken by a human being rather than being automated through fixed white/black listing settings

Note: This Feature is a purely a Feature of “Exchange 2010”. Thus in a coexistence Scenario of Exchange 2010 and Exchange 2007 we must send a message first to Exchange 2010 Hub Transport Server first because if the Exchange 2010 Hub Transport Server would not Receive the Email and Exchange 2007 Hub Transport Serer would Receive the email than the Hub Transport Server would expand the distribution list and bypass Moderation.

Now for example you want that when you Managers sent an Email to the Distribution Lists those have Moderation Enabled on them. Than while creating the Email Moderation Rule you can exclude the “Managers group” from this Email Moderation Rule