What should the PTR record be?

Question

Email

1. If the hoster's PTR is written as "domen.ru.", does this mean that the A record will be taken for this value?
2. If I write the ip of the mail server there, will it not disrupt the site?
3. What if you need to register both ip4 and ip6, and the input line is only 1 there?
And the most important thing:

SMTP error from remote mail server after end of data:
    host gmail-smtp-in.l.google.com [2a00:1450:4010:c05::1a]:
    550-5.7.1 [наш ip6] 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.

.
Will adding our ip6 to ptr solve the problem if we rewrite the entry "domen.ru."?

Answer 1

If your PTR is already registered in the domain name, and there is an AAA record for this name, then everything is fine with PTR, authentication is bad. GMail only accepts mail from IPv6 addresses if the mail passes SPF or DKIM authentication.