Email Not Sent to Exchange 2010 Distribution Group Member

I have a Distribution Group in Exchange 2010 that has an Active Directory SMTP Contact as a member. If I open Outlook 2010 and enter the Distribution Group in the "To" field, and right click and Expand the list, this member of the group is displayed with the correct email address. However, if I send an email to this group and check the Exchange logs using Power Shell, email is not sent to this member. What would cause this? Thanks in advance for your responses.