Greylisting — one more tool in the arsenal against SPAM

I ran across the following link the other day and was very interested.
Postfix and Postgrey: A proactive approach to spam filtering

For those not familiar with Postfix, it’s an MTA (Mail Transfer Agent). Basically, a mail server. It’s the server application that stores, accepts and sends emails to different mail servers. So Postfix is usually our first line of defense against SPAM. A few postfix plugins already help with spam but still many get through because spammers consistently change their techniques.

So greylisting is becoming more and more popular, and for good reason. After installed Postgrey, my personal spam dropped considerably. I don’t have any hard numbers, but I would say that a drop of 60-75% wouldn’t be too far off.

To illustrate, here’s the graph for the traffic from my mail server. I made it so the anything that was greylisted was labeled as spam in this graph (click for full size):

Mailgraph with Postgrey activate on Thursday

As illustrated, I added Postgrey filtering into the spam “bucket” on Thursday.

Thank goodness for smart people who have (and take) the time to solve the problems I have 😉

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