> How many messages come into a server for multiple recipients in the
> same domain? I guess if someone was mailing multiple people at the
> same company, it would happen. But with most mailing lists using
> custom bounce messages for each recipient, they wouldn't be affected.
> How about the spammers who email 100's of random usernames in a domain,
> hoping to hit valid addresses? The 4xx response would at least slow
> them down (and even stop them if their spam programs don't retry 4xx
We actually see a fair amount of messages come in for multiple valid users
under one domain. They're usually messages of the style "meeting at lunch"
and similar things, sent from some office manager to several staffers.
These are sometimes sent from home accounts (users don't have the best
Maybe it would be best to defer the messages after some number of
recipients? Something like accepting the first 5 or 10, the 4xx responses
for anything after that? I think I've only ever seen maybe two or three
*valid* messages with hundreds of recipients -- most of the valid messages
with multiple recipients seem to have less than about 10 recipients.
UNIX Systems Administrator