
<html><head></head><body bgcolor="#FFFFFF"><div>And, given this discussion, a trifle ironic, no?</div><div><br></div>Sorry, we were unable to deliver your message to the following address.<br><span></span><br><span><<a href="mailto:noel.butler@ausics.net" x-apple-data-detectors="true" x-apple-data-detectors-result="0">noel.butler@ausics.net</a>>:</span><br>Remote host said: 554 5.7.1 <nm3-vm1.bullet.mail.sg3.yahoo.com[106.10.148.112]>: Client host rejected: This network is currently not accepting Email from Yahoo [RCPT_TO]<div><br><div>On 10 Jan 2013, at 21:58, Lloyd Wood <<a href="mailto:lloyd.wood@yahoo.co.uk">lloyd.wood@yahoo.co.uk</a>> wrote:<br><br></div><div></div><blockquote type="cite"><div><span>MUST and SHOULD are defined in the later RFC2119.</span><br><span></span><br><span>RFC793 doesn't use them either.</span><br><span></span><br><span>And RFC2119 and 1912 are on the legacy RFC stream....</span><br><span></span><br><span></span><br><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span>RFC 1912, Section 2.1 says every Internet-reachable host should have a name</span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span>and "Make sure your PTR and A records match" and "For every IP address,</span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span>there should be matching PTR record in the in-addr.arpa domain"</span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span>its DNS 101</span><br></blockquote></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>Note that it is not a *MUST* requirement, nor even a *SHOULD*.</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>And, frankly, _depending_ upon PTR records in 2013 is just plain daft.</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>% host -t mx <a href="http://gmail.com">gmail.com</a></span><br></blockquote><blockquote type="cite"><span><a href="http://gmail.com">gmail.com</a> mail is handled by 30 alt3.gmail-smtp-in.l.google.com.</span><br></blockquote><blockquote type="cite"><span><a href="http://gmail.com">gmail.com</a> mail is handled by 40 alt4.gmail-smtp-in.l.google.com.</span><br></blockquote><blockquote type="cite"><span><a href="http://gmail.com">gmail.com</a> mail is handled by 20 alt2.gmail-smtp-in.l.google.com.</span><br></blockquote><blockquote type="cite"><span><a href="http://gmail.com">gmail.com</a> mail is handled by 5 <a href="http://gmail-smtp-in.l.google.com">gmail-smtp-in.l.google.com</a>.</span><br></blockquote><blockquote type="cite"><span><a href="http://gmail.com">gmail.com</a> mail is handled by 10 alt1.gmail-smtp-in.l.google.com.</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>% host <a href="http://gmail-smtp-in.l.google.com">gmail-smtp-in.l.google.com</a>.</span><br></blockquote><blockquote type="cite"><span><a href="http://gmail-smtp-in.l.google.com">gmail-smtp-in.l.google.com</a> has address 173.194.70.26</span><br></blockquote><blockquote type="cite"><span><a href="http://gmail-smtp-in.l.google.com">gmail-smtp-in.l.google.com</a> has IPv6 address 2a00:1450:4001:c02::1b</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>% host 173.194.70.26</span><br></blockquote><blockquote type="cite"><span>26.70.194.173.in-addr.arpa domain name pointer <a href="http://fa-in-f26.1e100.net">fa-in-f26.1e100.net</a>.</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>% host 2a00:1450:4001:c02::1b</span><br></blockquote><blockquote type="cite"><span>b.1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.2.0.c.0.1.0.0.4.0.5.4.1.0.0.a.2.ip6.arpa</span><br></blockquote><blockquote type="cite"><span>domain name pointer <a href="http://fa-in-x1b.1e100.net">fa-in-x1b.1e100.net</a>.</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>The lack, or mismatch, between advertised name and PTR records should</span><br></blockquote><blockquote type="cite"><span>just be used as a signal to a reputation service.</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>A recent post from someone who works in this area (disclosure; I don't</span><br></blockquote><blockquote type="cite"><span>use their service at this time) covers the kinds of signals you'd</span><br></blockquote><blockquote type="cite"><span>generally expect to us.</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span><a href="http://rolandturner.com/2012/12/14/a-defensive-strategy-for-accepting-email-over-ipv6">http://rolandturner.com/2012/12/14/a-defensive-strategy-for-accepting-email-over-ipv6</a></span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>I realise that this doesn't help the OP but I just wanted to ensure</span><br></blockquote><blockquote type="cite"><span>that people know that PTR records are a defining anti-spam mechanism</span><br></blockquote><blockquote type="cite"><span>are very outdated.</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>Regards,</span><br></blockquote><blockquote type="cite"><span>Anand</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>-- </span><br></blockquote><blockquote type="cite"><span>“Don’t be sad because it’s over. Smile because it happened.” – Dr. Seuss</span><br></blockquote><blockquote type="cite"><span>_______________________________________________</span><br></blockquote><blockquote type="cite"><span>AusNOG mailing list</span><br></blockquote><blockquote type="cite"><span><a href="mailto:AusNOG@lists.ausnog.net">AusNOG@lists.ausnog.net</a></span><br></blockquote><blockquote type="cite"><span><a href="http://lists.ausnog.net/mailman/listinfo/ausnog">http://lists.ausnog.net/mailman/listinfo/ausnog</a></span><br></blockquote><span>_______________________________________________</span><br><span>AusNOG mailing list</span><br><span><a href="mailto:AusNOG@lists.ausnog.net">AusNOG@lists.ausnog.net</a></span><br><span><a href="http://lists.ausnog.net/mailman/listinfo/ausnog">http://lists.ausnog.net/mailman/listinfo/ausnog</a></span><br></div></blockquote></div></body></html>