How to set up a PTR record for a local sendmail mail server on CentOS?

Question

send mail

Good afternoon. We are trying hard to defeat the spam filters of Yandex, Google and mail. There is a server with boxed Bitrix in the cloud. There is a domain tied to Yandex mail. Registered spf, dkim, dmarc in dns. return_path points to our mail.
As a result: Google does not accept letters at all, sends the mail to spam. It remains only to add ptr for the full set and it's not entirely clear how to do it.
Mail from domainname.ru, a server with Bitrix that sends letters to crm.domain.ru The
provider told us that letters should have an smtp-banner, and the provider will write the smtp-banner value for our IP.
What should the provider set for itself and what should we configure in the sendmail configs?

Answer 1

In general, in my case, it turned out that the machine with centos should have the name crm.domain.ru, and this is the ptr name that the entry is made

Answer 2

For a PTR record, contact your host.
Write spf entries, etc. not enough, did you check them for correctness? what's in the headers of the emails you receive? it says that everything is fine with spf and dkim?
At the present stage of mail exchange, it is better to use encrypted connections, for this you need to attach a certificate to your MTA, without encryption there is a very high probability of falling into spam.

Answer 3

Sendmail:
tanhaishi.blogspot.com/2011/11/warning-reverse-dns...
DNS:
PTR which resolves the server address to mail.example.com
But I highly recommend using sendgrid or another cloud mail service. https://sendgrid.com/pricing/ has up to 100 emails per day for free, and then inexpensively, and there is a simple integration with the clouds.