On Fri, 20 Aug 2004, Roy Badami wrote:
I'm ignoring spammers who send mail out through open relays; they're
unlikely to implement SPF checks, but you can hope to block many of
them through DNSBLs...
This isn't right. Not to /open/ the open relay question, but see
http://www.av8.net/openrelay.html
I realize that many people disagree with that, but courts and lawyers have
agreed with us. So, I won't argue this if you disagree. But if you didn't
know, it may be interesting.
For abusers, there is no difference between an ISP's closed relays and
open relays, unless they are self-described anti-spammers who think that
by abusing the relay they will get it closed or something. Closed relays
are "open" to those using the network's IP Address space. All abusers
everywhere have one or more relays available to them, because they are
"customers" right up until they aren't.
There is one difference between open and closed relays since the open
relay blacklists closed down: its not so easy to find open relays to
abuse. Though we and other ISPs found some time ago that blocking the
blacklist scanning stopped open relay abuse. But networks can't hide
their closed relays from their customers.
--Dean