SMTP test failed: Reverse DNS is not a valid Hostname. How can I fix it?

Question

Domain Name System

Domain: halje.ru
Created A record for level 3: mail.halje.ru
Created PTR record for: halje.ru, mail.halje.ru
Created MX record: halje.ru > 10
mail.halje.ru be this error? I don't know what else can be done.
In /etc/postfix/main.cf

#myhostname: mail.halje.ru
#mydomain: halje.ru
#myorigin: halje.ru

SCREEN FROM THE SITE MXTOOLBOX.COM

Answer 1

Created a PTR record for: halje.ru, mail.halje.ru

What is it like?
Suppose the ip of your mail server is SERVER_IP, then in order to correctly receive mail from your halje.ru domain, 3 DNS records must be created:
1) A - a record for the mail.halje.ru mail server with the SERVER_IP address
2) MX - a record for the halje domain. ru pointing to mail.halje.ru
3) PTR - entry for SERVER_IP pointing to mail.halje.ru
In addition, it will be useful to create spf, dkim and dmarc entries. How to do it is easy to google

Answer 2

PTR records are created for ip addresses, not domain names.
You most likely do not have a PTR zone and therefore you need to contact the provider that gave you external ip addresses, since it is he who most likely manages the PTR zone for them.
nslookup %ip address bound to mail.halje.ru%, what does it show?