On 1/14/2014 4:06 PM, Brandon Applegate wrote:
Just saw this in a message tonight. No idea if this is a transient error or not.
--- host gmail-smtp-in.l.google.com [gmail-smtp-in.l.google.com][2607:f8b0:4002:c01::1a] said: 550-5.7.1 [2607:ff70:11::11] Our system has detected that this message does not 550-5.7.1 meet IPv6 sending guidelines regarding PTR records and authentication 550-5.7.1 . Please review 550-5.7.1 https://support.google.com/mail/?p=ipv6_authentication_error [support.google.com] for more 550 5.7.1 information. t26si2290895yhl.255 - gsmtp (in reply to end of DATA command)
I saw a number of these as well but in my case the bracketed IP addresses were malformed. For example: host gmail-smtp-in.l.google.com[2607:f8b0:4002:c01::1a] said: 550-5.7.1 [2607:fc50:1000:1f00::2 16] Our system has detected that this 550-5.7.1 message does not meet IPv6 sending guidelines...