Why do letters leave in Exim4, but the remote server does not accept them?

Question

Exim

Good afternoon, comrades
I encountered such a problem, some mail servers do not accept mail from hosts whose MX looks at one IP, and PTR looks at another.
For example:
there is a host vasya.ru
#host -t mx vasya.ru specifies
vasya.ru mail is handled by 20 mail.vasya.ru.
#host mail.vasya.ru
mail.vasya.ru has address xxx1
But at the same time:
vasya.ru -- itself resolves to xxx2
When sending mail to certain hosts, an error occurs:
petya.ru[yyyy]: 450 4.7.1 Client host rejected: cannot find your hostname
, [xxx1]: retry timeout exceeded
vasya.ru - lies on shared hosting.
Does anyone know how to beat this? So that letters are delivered to all mail servers.

Answer 1

Your problem is not with finding IP by hostname, but with the reverse procedure.
You need to register a reverse zone for your domain and the corresponding PTR record should point to mail.vasya.ru
It is worth paying attention to the fact that this is done not where the vasya.ru DNS zone is serviced, but where you are provided with an IP for mail. vasya.ru, i.e. probably from a hoster providing you with a server or vps.

Answer 2

The PTR zone cannot be registered, because it is located on the shared domain, and accordingly, for each domain on 1 IP you cannot register a PTR record (
roughly speaking
xxx1 - it cannot be assigned as a PTR for mai.vasya.ru, kotya.murzik.ru domains etc etc...