[wplug-internet] Spam Filtering Set up

[Smith, Justin]

I beefed up on my mail server skills over the weekend and got Amavisd, 
SpamAssassin, and ClamAV set up on the server - I think.

There's a detailed documentation guide at /home/board/spam-filters.md 
that describes the basic setup. I invite you to read it; it describes 
what the components are, how to manage them, and how they fit together. 
But for convenience, I'll reproduce a small subset of that here:

- Postfix receives an incoming email.
- Postfix passes the message to Amavisd, which serves as a "bridge" 
between Postfix and the other services
- ClamAV scans the file and lets Amavisd know if it's infected with a 
virus
- SpamAssassin scans the file and generates a numeric score representing 
the "spamminess" of a message. Higher score = more likely to be spam.
- Amavisd decides what to do with the message based on the results of 
the above two steps.
    - You can have it do not nothing, quarantine, or delete/bounce emails 
that have been flagged as having a virus.
    - You define a base SpamAssassin score threshold at which point the 
words ***SPAM*** will be added to the subject line, but no further 
action taken
    - You can also define a "kill threshold" SpamAssassin score at which 
point messages can take some other action - quarantine or discard/bounce

For now, I've set SpamAssassin to delete any messages infected with a 
virus and merely flag messages that are flagged as having a spam score 
of 6.3. The spam kill threshold is set to 6.9, but the kill threshold 
action is set to "PASS" for now, which does nothing.

If we find that SpamAssassin does a good job of picking up spam, we can 
tweak the scores and/or adjust the kill action so that genuine spam will 
be dealt with automatically.

Let me know if you have any questions.

- Justin