This function checks if a value is a valid email address against certain 2-letter country or region codes and the following top-level domains:
If an email is flagged as "False," it may use a top-level domain that isn't on our list.
value- The value to be verified as an email address.
ISURL: Checks whether a value is a valid URL.
ISERROR: Checks whether a value is an error.
ISTEXT: Checks whether a value is text.
ISBLANK: Checks whether the referenced cell is empty.