advice on anti-spam tools

[Erik Norgaard]

Angelin Lalev wrote:
> Hi List,   
>   
> My e-mail server is running the latest spamassassin with all of the blacklist enabled and etc. 
> but I still receive over 20 spam messages a day ("image" spam mostly). 
> The situation with other users may be worse.  That's why I was thinking about some tool that 
> 1. store incoming email
> 2. send request to the sender of the message, requiring to go to some address and enter the numbers (letters) 
> from image
> 3. if the puzzle is solved in time (week or so) deliver the message, otherwise delete it.
> 
> Is there such tool(s) ?

I use grey listing and spamhaus xbl, no spamassasin or content analysis. 
Apart from grey listing and spamhaus, I block in my firewall IP ranges I 
have found un trustable, particular China and Korea, and ranges assigned 
dynamically, and I have some header analysis rules.

I get about 2 spam mails a day.

The earlier you can reject a message the less resources it takes, see 
how much you can reject on the envelope rather than data.

I have found that many spammers use my servers name or IP in HELO, so I 
reject that. Also, reject unresolvable domains etc, simple stuff.

Really, if you want to effectively address the problems, store all spam, 
create a spambox for users to forward their spam to. Analyse it every 
now and then. For example I did this to idenfity IP ranges sending spam.

With greylisting, I have found that greylisting 5 minutes will delay 
mail significantly and some mail will not be delivered. 3 minutes seems 
better.

Cheers, Erik
-- 
Ph: +34.666334818                      web: http://www.locolomo.org
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