[Mailman-Users] Reject non-members at SMTP time

[glen at prideaux.id.au]

Is there a way to reject non-subscribers at the time of their initial SMTP
conversation, as opposed to either rejecting them later (with an
associated bounce message) or silently discarding them?

I don't want to generate bounce messages because of the back-scatter they
generate, but silently discarding is also bad: non-spam senders should get
some notification that their message has failed.

I'm using exim4 and it seems likely that there is a way to have exim check
whether mailman is willing to accept the message at SMTP time.

Is this something that others have done? I thought it would have been a
fairly common requirement but I haven't been able to find any clear notes
on how to do it.

Glen