free antispam for Linux

[John Van Ostrand]

Jeremy Baker wrote:
> I use Maia Mailguard.  It is an amavisd based web frontend that uses 
> spamassassin and clamav to process incoming mail. Works great.
>   
The summary of all this is that generally most solutions use more than 
one technique for finding spam. SpamAssassin performs pattern matching 
in the email and meta data, greylisting and delayed banners check for 
impatient MTAs, RBLs look for known spammers or for hosts that shouldn't 
be sending email, OCR decodes images to look for words, razor and pyzor 
compare messages with a network of MTAs, spam traps capture spam and 
there are many more techniques.

One thing that I've learned is that there isn't a fire-and-forget open 
source solution. Each needs tuning and work to keep up. I tend to have 
to re-tune my solution (MailScanner) quarterly. I use RulesDuJour to 
keep spam assassin rules up to date daily, but I have to check for new 
rule sets manually. MailScanner comes up with new ways to detect spam so 
upgrading and reviewing it's changelog are valuable. Very rarely I will 
institute a new MTA method (like delayed banner) or turn on a new 
MailScanner feature.

In my case my server processes about 10,000 messages a day. About 5,000 
are refused before they submit the message. Of the 5,000 remaining about 
2,000 are spam.
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*Linux Solutions / IBM Hardware* 	Fx: 519-883-8533 	 

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