Deny send to dynamic distribution groups for certain users

In Exchange 2007 I need to prevent certain users from being able to send e-mail to a dynamic distribution group.  I don't see any option to set permissions on the group.
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zane_oAuthor Commented:
I found the setting.  Must have just not been looking.
It is under the Mail Flow Properties tab of the Dynamic Distribution Group properties.
Select Message Delivery Restrictions, Click Properties, under "Accept Messages From" you can choose "Only senders from the following list"
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