I'm assuming you setup the mail domain and users in ispconfig?
Assuming you are using postfix... take a look in /etc/postfix/main.cf and look for the line "mydestination="
If you have adrian.com.au in that line, then you are screwed :-) Postfix will think that's a local mailbox and not lookup the virtual tables in mysql for the domain and it's users.
How to fix? Well remove your domain from that mydestination = line, this will leave just localhost stuff left there. Then restart postfix.
Then, postfix should look up the virtual maps when an email arrives and find the mail setup you did in ispconfig.
If this doesn't work.. I need more info :-)