Quote:
Originally Posted by vasbinde
Another SPAM protection option that I use with great effect is the Challenge-response approach. It basically puts every single email I receive into a "likely spam" queue, then sends an email response asking for the person who sent the original email to verify that they are a real human being.
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There is much better system for filtering spam.
It is called greylisting.
It is similar to the system you describe, but it
does not bother the sender.
scenario:
mail is sent from YourRandomServer.com to MyServer.com
MyServer.com replies to YourRandomServer.com "I can not accept that mail in this moment, please try again later" (this happens quite often during the normal course of operation, not only if you implement greylisting).
MyServer.com makes a note that YourRandomServer.com has tried to send this particular message.
YourServer is a well behaved, standard compliant server (unlike the VAST majority of spam sending virus infected Windows PCs) so it tries to deliver the mail again.
This time MyServer.com receives the message, and adds YourRandomServer.com on the whitelist so the next time YourRandomServer.com sends a message, the message is received immediately.
I have implemented this on our company server and the spam that "gets through" has decreased to 5% of the original volume. Quick, simple, effective.