How to setup rDNS record for my mail server

Hi, hope all is well. I have 5 Website in one VPS (IP) and One Cyberpanel. My queston is how to setup Rdns for each one, my mail go to gmail spam, and is not sending to other mails. This is the wp mail plugin error:
2023-03-07 17:20:21 Connection failed. Error #2: stream_socket_enable_crypto(): SSL operation failed with code 1. OpenSSL Error messages:error:1416F086:SSL routines:tls_process_server_certificate:certificate verify failed [/home/domain.com/public_html/wp-includes/PHPMailer/SMTP.php line 468]

SMTP Error: Could not connect to SMTP host. Connection failed. stream_socket_enable_crypto(): SSL operation failed with code 1. OpenSSL Error messages:error:1416F086:SSL routines:tls_process_server_certificate:certificate verify failed

Happy New Year @BOOBA

rDNS ptr record is only set for the VPS i.e. the record identified the ip address against the hsotname. e.g. 123.456.789 server with primary domain genghiskhan.com would have its hostname as mail.genghiskhan.com and therefore its rDNS ptr record for both ipv4 and ipv6 ip addresses as mail.genghiskhan.com

Note: if the server does not have a rDNS record, it cannot resolve a reverse lookup.

You need to issue mailserver ssl certificate to say mail.primarydomain.com (this is the mailserver domain) any other email under this mailserver can and potentially should use mail.primarydomain.com as their mail domain. See cyberpanel configurations here https://SERVER_URL:8090/email/listEmails

I have 5 Websites in one VPS (IP) and One Cyberpanel. My question is how to set up Rdns for each one, or add the Rdns that work for all of them. Also i issue ssl for webmail and hostname. But it’s not working, always show not secure, certificate is not valid.

Kindly read previous reply. Read this further to understand Reverse DNS lookup - Wikipedia

Which server os is this? Do you have latest version of cyberpanel ?

Rdns for each one: Im not familiar, that’s why I’m posting here to get help. I have multiple domains in one VPS, and one cyberpanel. So, how i can add the Rdns on my vps, they only show one IP and One Rdns. Im using centos. I usse ssl, but alwyas not working. Now my mail go to gmail spam and i have 10/10 test mail.

To setup rDNS go to where you lease your server from and look for Reverse DNS Management (for help with contact your service provider) and add a ipv4 and ipv6 rDNS ptr record with the value mail.primarydomain.com for example

Yes, thank you, but this is not what i need, it’s not good to add mail.domain.com for all of my websites on my reserve dns server.