Exchange distribution group behavior when two groups have the same member

So how many domains do you have? How many users/computers/groups per domain?

Given your description I'd expect it's highly unlikely that you'll encounter any negative replication impacts from using strictly Universal Distribuion Groups for your DLs.

Thanks,

Brian Desmond

Active Directory MVP

A few ideas:

• You could set the groups as dynamic dist groups to prevent expansion, and set them up as moderated to prevent unauthorized mail.
  • Or just set a hard filter of allowed senders if that'll fly - but, that won't work for external users without disabling authentication.
• You can strip the reply-all button off of Outlook via group policy for internal users.

Nothing here stops users who know who's in the list from just sending mail to them.. but you can prevent casual exposure of that if it's non-trivial to expand the group to its members.