Preventing 'Reply-All' to Exchange Distribution Groups

Solution 1:

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.

Solution 2:

You could secure the DL so that only specific persons could send to it. I believe the relevant AD attribute is "dLMemSubmitPerms".

http://technet.microsoft.com/en-us/library/aa997251%28EXCHG.65%29.aspx

That would prevent a "reply all" to that group. And anyone can send to any specific recipient at any time anyway, so that should not be relevant to the requirement.

This should only be relevant in the narrow edge cases where someone forgot to put the group in the bcc field.