I got this info years back from some now dead site.

How to Filter Out Spam

Is your Message List pane being cluttered on a daily basis by
unsolicited commercial email (UCE) and other offensive messages? These
types of messages, commonly referred to as "spam", are a major
annoyance to many users. To eliminate as much spam as possible, use
this procedure:

1.Set up three folders, as follows:

·Create one folder is for email that you know you want to receive. You
might call it "inbox". (Of course, you could create multiple folders
to further categorize messages that you want to save.)

·Create a second folder for UCE/spam. You could call this folder
"trash". (Alternatively, you could configure your filters to delete
spam immediately upon receipt. The only problem with that approach is
that you might inadvertently delete a message that you really wanted
to keep.)

·Create a third folder for mail that has not yet been categorized. You
could call this folder "uncategorized" or "to be sorted".

2.Next, configure Agent's default email filter settings to use the
three folders:

·On the Inbound Email Folder tab (Options menu), select the default
folder to be your "uncategorized" folder. This will cause all email
that is not processed by any other filter to be placed there.
·On the Kill tab, set the File in Folder to be your "trash" folder.
You will probably find that the other dialog settings are already
appropriate.

·On the Watch tab, set the File in Folder to be your "inbox" folder.

3.When you first start receiving email, all new messages will get
filed in the "uncategorized" folder. After you receive a batch of new
messages, scan through them to decide how you want messages from the
same senders to be processed in the future.

4.For spam messages, press Ctrl+K to create a kill filter using the
Add Email Filter dialog box. The default filter settings will create a
filter that will place all future messages from that sender in your
"trash" folder. For some good examples of expressions designed to
eliminate spam, see the topics Expression Examples.

By default, the kill filter will match the sender's complete email
address. That will often be appropriate. But, you might want to modify
the filter if you want to match any messages from that domain. For
example, if you receive a message from "great-offer@savetrees.com",
you could choose to trash all future messages from any address at the
"savetrees.com" domain. To modify the filter to match just the domain,
press the Paste Field button, highlight the "Any-Sender (Domain only)"
entry, and press OK. (Of course, you could achieve the same result by
manually editing the match expression; using the Paste Field button is
just faster.)

TIP: Many times spam mail is not directly addressed to you, that is,
it does not have your actual address as the value in the "To:" field.
One handy way to eliminate this type of spam is to create a kill
filter that will match any message that does NOT contain your actual
address. Here's an example for a user named Jane Doe:

not any-recipient:janedoe@abc.com
This will work for most spam. However, you may find that your own mail
system inserts an Apparently-To field into messages that are missing a
To: or Cc: field. The "any-recipient" filter matches the Apparently-To
field. If you'd prefer to have a filter that does not match that
either, try the following example:

not to: janedoe@abc.com and not cc: janedoe@abc.com

For messages from senders you know and want to receive messages from
in the future, press Ctrl+W to create a watch filter containing those
individuals' addresses, for example:

from: (tsmith@acme.com or hank.lloyd@zsu.edu or mjones@abc.com )
When you create either a kill or watch filter, you can check the
"Apply filters to folder immediately" option to cause Agent to reroute
all matching messages immediately. If you aren't sure that you want to
reroute *all* matching messages in the folder, you can check "This
message only".

As you define more kill and watch filters, you will find that Agent
will get better at automatically routing your email, and there will be
fewer "uncategorized" messages that you have to deal with.