What specific MX Record is needed to pass mail-tester.com verification?

Question

Mail server

Hello!
mail-tester.com writes to me:

We check if there is a mail server (MX Record) behind your domain name mydomen.com.
You may want to publish a DNS record (MX type) for the domain name mydomen.com or use a different bounce email address.

But it is completely unclear what kind of record he needs?
Please tell me what exactly you need to write in the DNS?
Thank you.

Answer 1

Duc is written in English in white - MX.