> My personal preference is to use RSS (see
http://www.mail-abuse.org) for
> open-relay blocking as it only lists relays which are known to have been
> used to propagate spam, and warn on ORBS. The false positive rate for ORBS
> is alarmingly high for me. You'd be surprised at the number of significant
> mail servers listed in ORBS.
I second that: Don't block mails from hosts listed in ORBS. Many people
will yell at you otherwise. ORBS would be a great thing, if some
postmasters wouldn't be so frighteningly stupid. Exim offers to add
headers for hosts listed in RBLs, which I recommend instead. If you
get regular mail with such headers, make sure the responsible postmaster
knows what's up. Don't be afraid to tell him that his system is being
actively abused to relay spam, because usually it is.
Of course the funniest thing are complaints about open relays that you
don't run (note: traceroute does not tell you who to complain to) with
RBL warnings, because the sender runs an open relay. :)
Michael
