Problem sending mail from VDS to gmail.com. How to decide?

Question

gmail

Good time. When sending emails to gmail.com, I get the error
This message was created automatically by mail delivery software.
A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed:

логин@gmail.com
    SMTP error from remote mail server after end of data:
    host gmail-smtp-in.l.google.com [2a00:1450:4010:c0f::1a]:
    550-5.7.1 [2a02:f680:1:1101::fe] 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 https://support.google.com/mail/?p=ipv6_authentication_error for more
    550 5.7.1 information. pe3si14937587lbc.163 - gsmtp

after reading a little, I sort of realized that there was a problem with PTR (reverse record)
ispmanager 5, debian 7,
I added entries to Domain Names (DNS):

mail.sait.ru. 3600 PTR (reverse entry) 194.xx.xxx.xx
smtp.sait.ru. 3600 PTR (reverse entry) 194.xx.xxx.xx
sait.ru. 3600 PTR (reverse record) 194.xx.xxx.xx

rebooted the server .. NOTHING .. Tell me how you can solve the problem, maybe I'm doing the recording incorrectly? Thank you

Answer 1

xxxxin-addr.arpa.
this is how a valid PTR should look like

Answer 2

In this case, you really have a problem with PTR, but not with IPv4, for which you tried to set PTR, but, as Mystray correctly noted, with IPv6. Previously, Gmail did not put letters from IPv6 addresses without PTR into spam, but already for seven months it stopped accepting them en masse.
As far as I can see your VPS has IPv6 2a02:f680:1:1101::fe and PTR you need to register for it. You also need to add an AAAA record (direct DNS record for IPv6, i.e. one that converts a domain name to an IPv6 address) pointing to 2a02:f680:1:1101::fe for the domain that will be registered in the PTR (i.e. If you write mail.sait.ru in the PTR, then the subdomain should have an AAAA record pointing to 2a02:f680:1:1101::fe).
Plus, I highly recommend adding at least an SPF record for the domain from which the sending is taking place, to form it, you can contact those. hosting support. And DKIM would be nice too. It can be enabled via IPSmanager and added to the DNS TXT record that it will generate (if there is a "domain names" section in ISPManager, you can see it there).
Well, or as Mystray said, disable IPv6 in the mail server settings.