Exchange handle of NDR returned to a list.

["Roger Vicker, CCP" <rv-tech@xxxxxxxxxx>]

I am trying to figure out why the users are not receiving NDR notices
that they should.

An application on Server4 sends emails via smarthost ES01 (Sonicwall
Email Security appliance) with a return address that is a distribution
list name in Exchange.
Exchange is on Server1.

The ES01 will send back a NDR if the domain is invalid. We have
specifically tested with external domains that send a NDR when the user
is unknown.

If a user sends to the invalid address (either part) they get a NDR to
their individual inbox. However, if the application sends to the same
address the list appears to never receive the NDR or distribute it to
the individual member inboxes.

Does Exchange refuse NDRs to distribution lists? It appears to be that
or something in how the application is sending the emails that is
preventing the NDRs from being delivered. I have looked at the delivered
emails headers and everything appears to be there that would be needed
to return to the list.

Roger Vicker, CCP