Clarify MX records

Author: bbiggerr

openapi.yaml

@@ -16938,7 +16938,8 @@ components:
 
             `NS`: The subdomain, if any, to use with the Domain of the Record.
 
-            `MX`: The mail server subdomain. Must be an empty string (`""`) for a Null MX Record.
+            `MX`: The mail subdomain. For example, `sub` for the address `[email protected]` under the `example.com`
+            Domain. Must be an empty string (`""`) for a Null MX Record.
 
             `CNAME`: The hostname. Must be unique. Required.
 
@@ -16966,8 +16967,8 @@ components:
 
             `MX`: The mail server. Must be a valid domain unless creating a Null MX Record. To create a
             [Null MX Record](https://datatracker.ietf.org/doc/html/rfc7505), first
-            [remove](/docs/api/domains/#domain-record-delete) any additional MX records, then enter an empty string
-            (`""`) for this property. If a Domain has a Null MX record, new MX records cannot be created. Required.
+            [remove](/docs/api/domains/#domain-record-delete) any additional MX records, create an MX record with empty strings
+            (`""`) for the `target` and `name`. If a Domain has a Null MX record, new MX records cannot be created. Required.
 
             `CNAME`: The alias. Must be a valid domain. Required.