There are no headers named anything containing the word status, however the http response code of the request is 522, and if I view the request in a separate tab, the message that accompanies it is 'Connection timed out'.

Thanks, I think I understand. So if the target of the mx records (mx01.1and1.co.uk.) was actually (mail.example.com.) it would affect it, otherwise it wouldn't. Is that right?