Re: FW: ... the technique of Nolisting -- MIDRANGE-L

I'm not buying it. Spammers don't give a &(^% about RFC compliance.Often they start at the bottom of your MX records anyway because in manycases those don't have full spam protection and their nefarious crud ismore likely to get past you. In addition they often try other addressessuch as 'mail.yourdomain.com' because often those addresses are set upto allow inbound mail by authenticated users. Turns out though thatoften these will also accept mail destined for your domain withoutauthentication and again the spammers win.

This also puts additional load on mail servers around the net as theyattempt to get to the non-responsive server in the first MX. although inthis regard it's much the same load as Greylisting adds.


- Larry

Graap, Kenneth wrote:

I thought this was worth sharing with everyone...

Kenneth

****************************************
Kenneth E. Graap

IBM Certified Specialisti5 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)."