FW: ... the technique of Nolisting

I thought this was worth sharing with everyone...

Kenneth

****************************************
Kenneth E. Graap
IBM Certified Specialist 
i5 Professional System Administrator
NW Natural (Gas Services)
keg@xxxxxxxxxxxxx
Phone: 503-226-4211 x5537
FAX:    503-721-2518
****************************************

-----Original Message-----

An anonymous reader writes with the technique of Nolisting, which fights
spam by specifying a primary MX that is always unavailable. The page is
an
extensive FAQ and how-to guide that addressed the objections I
immediately
came up with. 

http://www.joreybump.com/code/howto/nolisting.html

From the article: 

"It has been observed that when a domain has both a primary (high
priority,
low number) and a secondary (low priority, high number) MX record
configured
in DNS, overall SMTP connections will decrease when the primary MX is
unavailable. This decrease is unexpected because RFC 2821 (Simple Mail
Transfer Protocol) specifies that a client MUST try and retry each MX
address in order, and SHOULD try at least two addresses. It turns out
that
nearly all violators of this specification exist for the purpose of
sending
spam or viruses. Nolisting takes advantage of this behavior by
configuring a
domain's primary MX record to use an IP address that does not have an
active
service listening on SMTP port 25. RFC-compliant clients will retry
delivery
to the secondary MX, which is configured to serve the role normally
performed by the primary MX)."