Help with a rule

[Yusuf Ahmed]

Hi,

Wondering if someone can give me a hand writing a rule. I'm kind of new 
to this and so running into a few problems.

SCENARIO: I am the owner of "sample.com.au". I have email accounts named 
"info" and "joeblow", therefore their email addresses would be 
[EMAIL PROTECTED] and [EMAIL PROTECTED]
PROBLEM: I am getting tonnes of spam coming through to random email 
prefixes @sample.com.au. I would like to block all email sent to 
@sample.com.au except for the email addresses specified above.

How would I write a rule for this? I'm assuming Meta rules are what I am 
looking for but need a bit more help.

Thanks.

Regards,
Yus.