advice on anti-spam tools
norgaard at locolomo.org
Sun Apr 8 17:16:32 UTC 2007
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
Ph: +34.666334818 web: http://www.locolomo.org
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