MX record - mail.site-name.ru, is it correct to point to a non-existent subdomain?

Question

Domain Name System

Good day, dear experts.

The hosting DNS has such a record mail.site-name.ru , but in fact this subdomain is not on the site.
And the moment, which is second, but also touches on this issue. When generating SSL, it is possible to check the box to generate a certificate for this subdomain as well. But I didn't do it, but generated it only for site-name.ru and www.site-name.ru
What kind of mail subdomain is this? In fact, it does not exist and no SSL certificate has been generated for it. But does it work? I would like to clarify this point for myself.

Answer 1

For mail.site-name.ru, an A record was created in the dns, which points to the ip address of the mail server.

Answer 2

Do you need to receive mail for your domain? If yes, to your server? If so, is the ip address of this server specified as an A record for the mail subdomain? If yes, then everything will work. If you do not need to receive mail, then you do not need an mx record at all