Office 365 domain registered

[김민정 null]

Office 365 will be registered with the domain only.

The mail server is using Google.
Adding MX records to confirm Domain Validation.
Mail is not available since then.
What should I do?

please help me!! :(

[#2]

Why don't you use the TXT record method instead of MX record?
In any case you don't need to remove all other MX records just to use that method to validate - you can keep the others and simply add the new one for validation.

[#3]

Agree here with Loryan. MX verification disrupts your mailflow immediately and maybe that is not what you want or need. TXT imho is 100% the way to go