Cannot send to gmail IPv6 PTR Records

Hello
I have an old server with centminmod.
I just got another new server with the latest beta of centminmod.

My custom_config.inc file has the following code

Code:

MARCH_TARGETNATIVE='n'
NGINX_SSLCACHE_ALLOWOVERRIDE='y'
SET_DEFAULT_MYSQLCHARSET='utf8mb4'
ZSTD_LOGROTATE_PHPFPM='y'
NGINX_LIBBROTLI='y'
NGXDYNAMIC_BROTLI='y'
PHP_PGO='y'
LETSENCRYPT_DETECT='y'
DUALCERTS='y'
PHPMSSQL='y'
PHPMSSQL_ALWAYS='y'
DISABLE_IPVSIX='y'

The file /etc/sysconfig/network has only NETWORKING=yes

when my website send emails to gmail (not all the time) i got the following error
Reporting-MTA: dns;
X-Postfix-Queue-ID: 1F7CE2B55AE3
X-Postfix-Sender: rfc822;
Arrival-Date: Fri, 22 May 2020 19:16:50 +0300 (EEST)

Final-Recipient: rfc822;
Action: failed
Status: 5.7.1
Remote-MTA: dns; aspmx.l.google.com
Diagnostic-Code: smtp; 550-5.7.1 [2a01:4f8:241:21d7::2] Our system has detected
that this message does 550-5.7.1 not meet IPv6 sending guidelines regarding
PTR records and 550-5.7.1 authentication. Please review 550-5.7.1
Prevent mail to Gmail users from being blocked or sent to spam - Gmail Help for more information 550
5.7.1 . e10si4530780wrj.486 - gsmtp

Lets say that we have 2 domains (Domain1.com and Domain2.com)
The website is visible only to domain2.com and the domain1.com redirects to domain2.com
Both domains are on cloudflare.
SPF records for both domains has the new server ip address.

all emails from website (phpmailer) are sent without authentication and from domain1.com
the domain2.com does not have any emails.

The old server didn't have those errors.

---

Does anybody know how can i resolve those ptr errors?

The old server had Centos 6 and the new has Centos 7