Hi
Closed lists will just be more efficient. If the bounce message is clear
then most genuine contributors will get that and respond appropriately.
I've only dealt with one real, actual problem as a moderator and it was
purely accidental that the offender wasn't a subscriber and I was able
to catch it. We should expect some spammers to join but even this hurdle
will eliminate the majority and we can boot any subscribed spammers
quite quickly.
ATB
Stevie