When google mail is not delivered

videlicet, @gmail.com shows status

Our system has detected that
    550-5.7.1 this message does not meet IPv6 sending guidelines regarding

therefore, all, what you need -
add such records to dns-zone AAAA

1. hostname - <name of your website>
2. IPv6-Address - <your ip6 address>
3. TTL - 3600
   
   +
    
4. hostname - www
5. IPv6-Address - <your ip6 address>
6. TTL - 3600

id est

your  /var/named/pri.site.com combination should be looking like

$TTL        3600
@       IN      SOA     dns1.server.name. site.com. (
                        2020052403       ; serial, todays date + todays serial #
                        7200              ; refresh, seconds
                        540              ; retry, seconds
                        604800              ; expire, seconds
                        3600 )            ; minimum, seconds
;

subdomain 86400 A        1.2.3.4
mail 3600 A        1.2.3.4
site.com. 3600 A        1.2.3.4
www 3600 A        1.2.3.4
site.com. 3600      AAAA        123:c080:140:42a6:500:2ff:fe9e:f50
www 3600      AAAA        123:c080:140:42a6:500:2ff:fe9e:f50
site.com. 3600      MX    10   mail.site.com.
site.com. 3600      NS        dns1.server.name.
site.com. 3600      NS        dns2.server.name.
default._domainkey.site.com. 3600      TXT        "v=DKIM1; t=s; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDV6kJha1eS++c5IZslupDKpSdmHjFQqlyNM+ZZ2g47qu6HMFvil9tO5hxwCKe8TWlFar11srHjnNGvJHCkBCbvCnDGjKu6ssiXOYqED4hPeskjsa/3APgCAvZgAx8whyXAyjmB1r6NKFNqKku0BqVKyxP2KHEOlEFNPBuicm6KnwIDAQAB"
site.com. 3600      TXT        "v=spf1 mx a ~all"