- 550 error for ipv6/PTR ?

Franck Martin fmartin at
Wed Jan 15 18:14:16 UTC 2014

On Jan 15, 2014, at 10:05 AM, Darren Pilgrim <nanog at>

> 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
>> [][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
>> [] 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[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...
Additional guidelines for IPv6

The sending IP must have a PTR record (i.e., a reverse DNS of the sending IP) and it should match the IP obtained via the forward DNS resolution of the hostname specified in the PTR record. Otherwise, mail will be marked as spam or possibly rejected.
The sending domain should pass either SPF check or DKIM check. Otherwise, mail might be marked as spam.

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