Can't change sender email to match new domain, what to do?

so I bought a new domain yesterday but I’m unable to change my sender email to match it.

my site is RoyalFitFinancial.net now and I had to change my sender email back to Info@RoyalFitLLC.com.

i changed it to Durant@RoyalFitFinancial.net so it would match my business but nothing would come through when testing the contact form.

I also manually sent an email to it and it says “address not found”

You have no mx record on the RoyalFitFinancial.net. You only have an A record.

This means there is no mail setup for this domain.

What does that mean?

I am sorry, either something has changed or the tool I used was faulty. I do see the mx record.

I still don’t understand what that is. Is that a coding term? If it’s coding, I can fix it but I’ll need detailed instructions to do it.