I concur, in fact I see them come in at precisely the wrong order, lowest preference first in the hopes that we're not running spam filtering on those particular hosts. I have found that putting a bogus mx record at lowest preference slows stuff down though. One of my services is for a company with about 150 mboxes, and I receive no less than 1.5mill spam emails a month for it. -----Original Message----- From: Paul Vixie [mailto:vixie@isc.org] Sent: Thursday, 17 December 2009 11:48 AM To: nanog@merit.edu Subject: Re: DNS question, null MX records Douglas Otis <dotis@mail-abuse.org> writes:
If MX TEST-NET became common, legitimate email handlers unable to validate messages prior to acceptance might find their server resource constrained when bouncing a large amount of spam as well.
none of this will block spam. spammers do not follow RFC 974 today (since i see a lot of them come to my A RR rather than an MX RR, or in the wrong order). any well known pattern that says "don't try to deliver e-mail here" will only be honoured by friend people who don't want us to get e-mail we don't want to get. -- Paul Vixie KI6YSY