[Mimedefang] Failed looping spam

[Les Mikesell]

> From: Tom Horan
> 
> Yes, getting a list of valid smtp address from Exchange onto my sendmail
> boxes wouldnt be a problem.
> 
> So if spam=true, and user=notexist then drop, else relay.

You can do this with the sendmail 'access' facility as well and
reject them immediately.  I've used an 'outside/inside' pair
of servers long before adding filtering and have had enough
turnover in the company to get a lot of undeliverable mail
that the outside relay accepts, then tries to return and of
course all the spam is from unreachable addresses.  I reduced
this a lot by periodically grepping the outside relay logs
for the 'no such user' error generated by the inside server's
rejection and turning these addresses into access rules like
user at domain ERROR:550 user unknown
and rebuilding the database.  You do have to pay attention
when someone who has been removed comes back, though.

  Les Mikesell
    les at futuresource.com