gmail.com - 550 error for ipv6/PTR ?

Wed Jan 15 18:05:50 UTC 2014

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...