How to set up email encryption on Laravel via a remote mail server?

Question

postfix

There is a configured website domain.ru and a mail server mail.domain.ru.
Letters from it are signed with a TLS certificate.
From another domain.by domain, I connect remotely to the mail one and send it.
But the letters go to spam because there is no encryption, due to the fact that the domain cannot be verified.
Do you need a new certificate and add domain.by there? Or in DNS it is necessary to register an additional domain to the mail one?

Answer 1

It is incomprehensibly written, leading questions:
1. The TLS certificate does not particularly affect the delivery of mail. Perhaps you mean DKIM signature?
2. Sending from another domain, what is meant by this, sending "mail from: [email protected]" via mail.domain.ru? Then most likely SPF&DKIM needs to be updated if you are the owner of domain.by.