Returns valid when Null MX record is set

[bmcculley]

What is this feature about (expected vs actual behaviour)?

RFC 7505 specifies "null MX" for when a domain explicitly does not support email.

Even if a null MX record is set this check will still return that the address is valid.

How can I reproduce it?

$emailCheck = EmailCheck::isValid("[email protected]", false, false, false,  true);

// expected false
// got true

Does it take minutes, hours or days to fix?

In isDnsError instead of using checkdnsrr it could use dns_get_record and then check the priority.

Any additional information?