They have been doing this for ages (maybe 6 months at least). We had to disable IPv6 on our mail server as we were struggling to get rDNS delegation from Orcon. Got too busy to follow up on it but will do so when I get a minute. Jonathan Spence Chief Executive Officer Fixed: +64 9 9510448 Mobile: +64211055634 ---------------------------------------- From: nznog-request(a)list.waikato.ac.nz Sent: Sunday, January 26, 2014 12:01 PM To: nznog(a)list.waikato.ac.nz Subject: NZNOG Digest, Vol 133, Issue 14 Send NZNOG mailing list submissions to nznog(a)list.waikato.ac.nz To subscribe or unsubscribe via the World Wide Web, visit http://list.waikato.ac.nz/mailman/listinfo/nznog or, via email, send a message with subject or body 'help' to nznog-request(a)list.waikato.ac.nz You can reach the person managing the list at nznog-owner(a)list.waikato.ac.nz When replying, please edit your Subject line so it is more specific than "Re: Contents of NZNOG digest..." Today's Topics: 1. heads up.. gmail now checking ipv6 rdns (Blair Harrison) 2. Re: heads up.. gmail now checking ipv6 rdns (Scott Howard) 3. Re: heads up.. gmail now checking ipv6 rdns (Michael Fincham) 4. Re: heads up.. gmail now checking ipv6 rdns (Phil Regnauld) ---------------------------------------------------------------------- Message: 1 Date: Sat, 25 Jan 2014 13:43:28 +1300 From: Blair Harrison <nznog(a)jedi.school.nz> To: NZNOG <nznog(a)list.waikato.ac.nz> Subject: [nznog] heads up.. gmail now checking ipv6 rdns Message-ID: <CAHn0gTveE=Nh-jp9Lfdw67UDAy=4Y-rgi-4h7t8zr1R_4p73zg(a)mail.gmail.com> Content-Type: text/plain; charset="iso-8859-1" Hi Folks, Just got caught out with this on my personal box today. It looks as if Gmail is now checking RDNS on any inbound ipv6 smtp connections and rejecting with 500 error if it doesn't match. example fail - SMTP error from remote mail server after end of data: host gmail-smtp-in.l.google.com [2a00:1450:4008:c01::1a]: 550-5.7.1 [2402:6000:1000:x::x] Our system has detected that this message does 550-5.7.1 not meet IPv6 sending guidelines regarding PTR records and 550-5.7.1 authentication. Please review 550-5.7.1 https://support.google.com/mail/?p=ipv6_authentication_errorfor more 550 5.7.1 information. oq6si4802967bkb.182 - gsmtp So if you have ipv6 enabled on your mail servers and haven't yet set some RDNS for them.. now is the time. Cheers, Blair