HQJaTu writes: > Google chose to change the wording in their 550 error. > 550-5.7.1 [2001:-my-IPv6-address-here-16] Our system has detected > 550-5.7.1 that this message does not meet IPv6 sending guidelines regarding > 550-5.7.1 PTR records and authentication. Please review > 550-5.7.1 https://support.google.com/mail/?p=ipv6_authentication_error > 550 5.7.1 for more information. dj7si12191118bkc.191 - gsmtp
Thanks for this information! That page now clearly states: 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. IMO, instead of working on workarounds, people's efforts would be better spent on setting up their DKIM and/or SPF, reverse DNS mapping, and making sure that postfix only binds to an intentionally configured IPv6 address (not on SLAAC or 'privacy extensions' random address). Mark
