How to fix [Error: Connection timeout] code: 'ETIMEDOUT' error on mail server?

Question

Mail server

On the site we use a mail server from Yandex to send orders to the mail.
During the test, a problem arose - letters with orders did not come to the right mail.
And everything works on the local server. Combat version on Amazon.
The mail server at this moment gives [Error: Connection timeout] code: 'ETIMEDOUT'
Sometimes letters skip sometimes not. There is an assumption that there is a limit on the number of letters in time? But there are not hundreds or even dozens of them.