Can you clarify what you mean by "doesn't match"?  Just the usual forward-must-match-reverse, or something else like EHLO matching?


On Jan 24, 2014 4:43 PM, "Blair Harrison" <> wrote:
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 [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 for 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.


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