PTR and other settings for “not getting” emails into spam?

Question

Exim

Setting up a PTR record assumes that the domain specified in the email headers is being revoked at a specific IP address. Do I understand correctly that if I have several sites on the same IP address (since they are on the same server), then I can configure PTR for only one of them?
And then I made a PTR for one domain, but I can’t specify my other domains (from which my scripts also send service letters).
What else can be tweaked in the exim4, DNS settings so that letters do not end up in spam (otherwise, now they don’t even end up in spam on my Yandex and Google)? You know about DKIM, but what else? EHLO or something else?
It is assumed that no mailings will be carried out from the sites, everything is much more banal: letters with a link to activate an account, password reminders, etc.
I clarify that the MX records of my domains point to mx.yandex.ru., since I use Yandex traffic rules to receive emails.

Answer 1

Do I understand correctly that if I have several sites on the same IP address (since they are on the same server), then I can configure PTR for only one of them?

Yes

What else can be tweaked in the exim4, DNS settings so that letters do not end up in spam (otherwise, now they don’t even end up in spam on my Yandex and Google)? You know about DKIM, but what else? EHLO or something else?

DKIM and SPF are enough.
EHLO? Haven't you done this before? In EHLO, you must give the same thing that is written in the PTR.

Answer 2

sorry, didn't read it.

I clarify that the MX records of my domains point to mx.yandex.ru., since I use Yandex traffic rules to receive emails.

DKIM and SPF should be configured based on where you're SENDING mail from, not where you're receiving it from.

Answer 3

> Do I understand correctly that if I have several sites on the same IP address (since they are on the same server), then I can configure PTR for only one of them?
PTR has nothing to do with domains, it has to do with the mail server, that is, the server name must match the reverse zone specified in the PTR.