How to fix an error when sending emails to @mail.ru?

Question

Email

There is a mail server on Mdaemon. When sending letters (the problem appeared from 06/02/18) from your domain to the @mail.ru domains, a thump comes:
550 Sorry, we do not accept mail from hosts with dynamic IP or generic DNS PTR-records. Please get a custom reverse DNS name from your ISP for your host xxxx or contact [email protected] in case of error
Before that, everything worked without problems for a year, DKIM, SPF, DMARC, PTR are configured, nothing has changed, there are no problems with other mail services. Our domain is not in the spam lists. Mail.ru tech support responded:
"The problem is that writeback (PTR) for your IP
is similar to writeback for IP dynamic networks, from which we do not
We accept mail in order to combat spam. You need to contact
your provider to change the PTR - so that it matches
your domain name."
After a repeated request to the support service with screenshots that everything is available and everything is spelled out correctly - 2 days no answer. What would you advise me to do or where to write?
PS we have about 400 mailboxes, a large sales department, etc. accordingly, this is a very acute problem that requires a quick solution, and not like @mail.ru technical support does
.

Answer 1

The problem was solved by technical support.

Answer 2

Well, ask the owner of the reverse zone to prescribe a more heroic PTR for you, not like a dynamic one.
Business for one letter

Answer 3

Hee hee hee. mail.ru is such a horrible monster that just put an enormous bolt on all postal standards.
You either do what she told you, or you don't write there.
I looked at your name. Most likely, either the "three dots" filter works there (it looks like, for example, "static-host-68-169-161-238.VALOLT2.epbfi.com") or the text "ppoevt".
mail.ru will not change anything because of you. He just put it on your office :)
JFYI: It's bad form to publish your real IP.