On Wed, 5 Mar 2003, Craig H. Block wrote:

> I'd like to look into using a mail filter like Spam Assassin.  I don't
> know much about them or what is available for Linux and Sendmail.  Can
> anyone give me some tips?

I personally use tmda (http://tmda.net). You can set it up per-user, or
globally. It's basically a whitelist-confirmation system with
cryptographic tokens for temporary or keyword-based revokable addresses.

I still get a few spams to deliberately unprotected addresses (such as my 
business accounts), but I get *no* spams at all to my personal accounts, 
and (once I worked the kinks out) no false positives at all.

Of course, this doesn't really reduce the traffic to the server from spam. 
For that, I use various rbl domains:

    relays.ordb.org
    relays.osirusoft.com
    sbl.spamhaus.org
    dsn.rfc-ignorant.org
    postmaster.rfc-ignorant.org
    abuse.rfc-ignorant.org
    whois.rfc-ignorant.org  

The first three are pretty reliable. The rest sometimes give false
positives, so use them advisedly.

If you're paying for bandwidth, you want to deal with spam before the SMTP
accepts the message for delivery, not after. Postfix is probably the most
efficient in terms of reducing spam-related bandwidth to the server, and
qmail the worst. Others fall somewhere in between.

Oh, and while it's deliberately flouting netiquette, I also typically
block entire netblocks from Asia which are simply spam clearinghouses,
such as .kr (202.0.0.0 - 203.255.255.255). I found that over 90% of my
spam was coming from APNIC netblocks, which are a real pain to
investigate. Life has been much easier since Korea has found itself
black-holed here. :)

-- 
"Of course I'm in shape! Round's a shape, isn't it?"

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