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However, the volume of spam continued to increase, almost as inevitable as the rising tide. I didn't let it bother me too much, as I could simply delete the messages sent to my spam folder, although I had to admit that looking through all of those messages for false positives was getting a bit tiresome.
And then it happened... The event that moved me past the tipping point, and thrust me forcefully back tot he front lines of the war on spam. The event seemed innocent enough: I went to send an email, and our smtp server (qmail) did not respond. wtf?
I shut down qmail, restarted it, and it seemed to work for a while. However, after an hour or so, the same problem arose. wtf?
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Why so many? Because for every spammer that sends an email to a bogus address, a mail server will craft a bounce message and attempt to send it back to the (usually faked) sender. Gah!
As a first step, I decrease the queue lifetime to 24 hours. After 24 hours, any message still left undelivered in the queue would now be deleted. Then, I cleaned out the queue and restarted qmail. It worked!
...for a while. Ok, so let's do some more furious reading on the subject of spam prevention in the qmail environment. First of all, I needed to increase the maximum number of qmail-smtpd processes which were allowed to run simultaneously by tcpserver. By adding a "-c 400" to the tcpserver command used to execute qmail-smtpd, I increased the maximum number of simultaneous connections from 40 to 400. That ought to be a good start.
Now, how else can I decrease the volume of spam? I had heard of greylisting before, and thought that it might be a good next step. Luckily, there is a simple greylist implementation for qmail called qgreylist. It installs fairly quickly, and does a fairly good job. However, it is written in perl and with all of the spam emails flowing in, it can cause a bit of a performance hit.
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With the above changes made to our mail server, I am now receiving about 10% of the spam volume that I was before the changes were made. Furthermore, our remote queue sits at a fairly steady level of 400 messages.
Only time will tell for how long this solutions will suffice! Wish me good luck and my email godspeed!