Why did the letters take a long time to reach the addressee?

Question

linux

Hello colleagues!
There was a problem with mail.
The mail.ru and yandex.ru servers, when receiving letters from my mail server, began to issue:

Result: delayed, Status: 4.3.2 451 Rate limit exceeded

As a result, the letter reaches 2-5 hours.
In my opinion, this is due to those. restrictions on sending letters to mail.ru and yandex.ru
Please tell me "how to send letters correctly"

Answer 1

As far as I remember, both services have instructions on "how to set up MTA" so that letters reach us without problems.

Answer 2

send the addressee to school ;)
Seriously - write to support mail.ru and Yandex