To sign up for Yandex.Mail for Domain:
You must have a Yandex account in order to use Yandex.Mail for Domain. You can connect up to 50 domains per account. Register if you haven't done so yet.
Make sure that your domain is ready to work with Yandex.Mail for Domain:
Register the domain with a company that provides such services, if you have not done this yet (Yandex can't register your domain).
Delegate your domain to the servers of the company that is providing DNS hosting.
You can delegate the domain to Yandex servers to automatically connect it to Yandex.Mail for Domain and manage DNS records through the service's interface. However, you must add the domain to Yandex.Mail for Domain before you can delegate it to Yandex servers.
Confirm that you have full domain management access:
Add the domain to Yandex.Mail for Domain.
If you delegated the domain to Yandex servers, you don't need to perform any special confirmation.
If you delegated your domain to Yandex servers, the required MX record will be created automatically.