Sending emails from the server - does the recipient check the MX record in DNS?

Question

JavaScript

Hello!
I am new to server setup. But I took up this business, since hosting has continuous restrictions. Question:
I used mail for a domain from Yandex. To do this, I registered their nameserver at the domain. Incoming mail works well, I do not want to refuse it. But the outgoing one (I send through them via SMTP) is constantly marked as spam due to the same type. I send greetings to clients when they register and other naturally similar notifications.
The server can send mail without Yandex. But will the receiving servers check that Yandex is registered in the DNS of the domain in the MX record, and the sending comes from the main IP address of the domain? Will this "inconsistency" cause emails to be marked as untrusted or spam, or not accepted at all?
Thank you!

Answer 1

Will depend on the recipient's server. As configured by the administrator. For example, such large services as Symantec.Cloud never check for the presence of an MX record, do not check for PTR. There is more focus on DMARC (DKIM + SPF) and its own heuristic algorithm. So there is no universal answer.
As a beginner (novice, by the way) in mail system administration, you will have to optimize your infrastructure for the current requirements of mail servers. Such as the presence of PTR, SPF, the absence of addresses in the DNSBL lists, DKIM signing, the correct Hostname in the greeting, etc.
You can use the free mail-tester.com service to check how clean your mail is (by the way, it also runs the content through SpamAssasign).

Answer 2

Just write SPF and set up dkim. Then you can send from your own without being tied to Yandex, and not a single letter will be marked as spam.