"www.aussiedog.com.au"

Somehow spammers have got hold of the email address on this website and the owner is recieving heaps of emails from his email address via the site?
Nowhere on the site is the email listed, not on any page.

Weeks ago I tested the email by uploading a php file and sending emails directly through the browser. I thought I had deleted this file but now I am thinking maybe this is the culprit.

I cant remember what file it was to delete it. Does anyone know what I am talking about so I can check please?

If this is not the cause has anyone got any ideas. It seems to have the extention of my host on it too - it is an addon domain?