RE: Separate incoming mail into 4 categories

At 01:45 2007-01-06 +0800, DR. Lee - NS3 wrote:
>However maybe one can check the validity of my reasoning. What I think
>is that instead of thinking about how to get rid of the junk mails,
>maybe I should concentrate on thinking about the sender and recipent.

It's called whitelisting (or greenlisting for PC minded folks).  Common 
pre-test before subjecting messages to more rigorous spam filters.

>Basically I only need to pay attention to those with both sender and
>recipient are known to my system.

You'll still get plenty of spoofed malware coming from people you may know 
because malware often rummages through their saved mail and addressbook to 
get addresses.  As a result, the malware is more likely to come from 
someone you know or have communicated with before (at least via a 
discussion list).

>For those match neither, it is for bin straight away.

I would be extremely cautious of this policy.

>If it match from_list only, the mail could be for an ex-staff of the
>company.

Er, why not reject ex-staff at the MTA?  Set up the MTA error message to 
either report back the address of the person NOW performing those duties, 
or (better) provide a URL to a page with general information about who to 
contact.

>If it match to_list only, then it could be a new contact.