I have a distribution group with the members being other distribution groups of which some are hidden from the GAL. In Exchange 2007, I believe those hidden members were visible when expanding the group in the 'To:' field and they (the hidden groups and their members) received emails sent to the group. I'm not sure, but I think that either after we upgraded to Exchange 2010, or after a service pack or update, you can no longer see those hidden members when expanding the group and those staff that are members of the distribution groups that are hidden, don't receive the emails sent to the group.
Is this by design? Is there some way to keep some of the members hidden and still allow them to receive the emails sent to the group?