This has happened before. The server supporting this site seems to refuse to send emails to some domains. It appears that the domain name of bigpond is currently rejected.
Years ago Bigpond often got blacklisted at SpamHaus etc for not doing enough to stop relaying spam. Maybe they got paranoid and the notification looks too much like a deluge of spam.
I saw a documentary on the old system of communication called a letter, apparently involving a stylus referred to as a 'pen' which one would scribe with a medium called 'ink' upon sheets of paper. Then the paper is placed into the 'envelope' and the geographical destination and recipients name is scribed upon the 'envelope' and it is placed into the metal bin after affixing the properly configured value of 'stamps'.
Quaint idea, however rather sketchy bandwidth as I understood it could take up to a week for the doc to arrive at the destination.