First, shut off the proxy on the mailA record. It should be and not .
Then, for the MX record, put @ for the name, not mail. The MX record is for the domain at which you want to receive email, and points to the mail server.
I’ve just shut the proxy off, so the cloud is now grey.
In the MX record, I dropped in the @ symbol. It looks like that was corrected automatically to our domain name. Does that gel with what I should expect. I’ll attach an image here to be sure you can view.