Hi Pierre, On Sun, Jul 14, 2019 at 06:17:50PM +0200, Pierre Frenkiel wrote: > I tried with mail.mailutils, and I get the following error: > > << 550-5.7.1 [2a01:e35:8a7f:9c50:2e4d:54ff:fed0:5806] Our system has > detected that > <<< 550-5.7.1 this message does not meet IPv6 sending guidelines regarding > PTR > <<< 550-5.7.1 records and authentication. Please review > <<< 550-5.7.1 https://support.google.com/mail/?p=IPv6AuthError for more > information
If sending email to Gmail over IPv6 you absolutely require matching forward and reverse DNS and some email IP authentication mechanism such as SPF and/or DKIM. If you can't do this, disable IPv6 in your mail server either in general or when sending to Gmail (could be tricky because this affects Google Apps For Your Domain also, so you don't necessarily know all the domains). You will have an easier time over IPv4 as Gmail relax their SPF/DKIM requirement, though can still avoid unwanted trashing of your email by implementing SPF and/or DKIM. Cheers, Andy -- https://bitfolk.com/ -- No-nonsense VPS hosting
