Gmail - Is the other server responding too slowly?

Question

gmail

There is a VPS, CentOS (I also tried it on Ubuntu), VestaCP + a configured account for connecting to an smtp server.
Since yesterday, gmail does not want to connect to the smtp server:

Другой ваш провайдер электронной почты отвечает слишком медленно. Повторите попытку позже или обратитесь к администратору соответствующего домена.

The configs did not change, I reinstalled everything from scratch - I set up only this account - the problem did not go away.