How to send a mail to the RAAF Museum ?

Hi all,

the last half hour I tried to send a mail to the RAAF Museum in Australia, but it failed to send every mail. (raafmus (at) ozemail.com.au)

Maybe someone have an idea how I can send a mail to the museum?
Every mails I send comes back with the notice it is unable to deliver the mail…

Rgards
Nils