Message does not meet IPv6 sending guidelines regarding PTR 550-5.7.1 records and authentication
I use OS X Server (El Capitan) as my personal email server. Everything is configured correctly. Mail works great for every domain except google gmail. This has been going on for 2-3 years...when ever I send email to Gmail users I get "undelivered mail returned to sender" which explains "this message does not meet IPv6 sending guidelines regarding PTR 550-5.7.1 records and authentication".
How can this be fixed?
Mac mini Server (Mid 2010), OS X Server, null