http://imgate.meiway.com
Does exactly this, is extremely configurable and extendable.
One of the features of the underlying SMTP mail server software (postfix) is a feature/addon called "postgrey" that gets around the problem of legit vs. non-legit mail servers. It temporarily blocks the receipt of a message based on the triplet IP + sender + recipient (storing the combo in a database). If the remote server is a legit server it will queue the message and try again later at which time "postgrey" will see the triplet combo and permit the message thereby blocking zombies.
Postfix (the underlying MTA) runs only on *nix OS so it does require a learning curve but all software is free but can run on hardware that has become underpowered to runs MS OS's. Mine runs on a Dual Pent II 233 MHz with 384Mb ram.
Check it out.
Mike
----- Original Message ----- From: "Cycle Rider" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Tuesday, November 16, 2004 18:03
Subject: [IMail Forum] Anti-spam idea
What about a mail proxy server gateway placed in front of imail that would automatically block any incomming connection containing words such as "dsl" and "cable" in their reverse DNS or IP, if no attempt was made to authenticate via SMTP AUTH?
Most of the spam appears to come from people running mail servers on their broadband connections. Legitimate email would not come from them. So why not differentiate between our legitimate users who use SMTP Auth and illegitimate servers running on cable and dsl connections?
Imail would never have to see those connections. Let the proxy server block them.
Thoughts?
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