In part one of this tutorial looked at installing and configuring greylistd alongside Exim to help combat the evils of Spam. In this second part I will look at getting some information out of greylistd -- handy if you need to troubleshoot why the CEO's "urgent" message hasn't arrived yet!
Traditional methods of spam protection involve using Bayesian detection rules (usually via SpamAssassin) on messages after they have been accepted by your server. Most mail sysadmins may have encountered the constant cries from their users asking "can't you stop them sending it?". Of course you can't stop somebody sending a message but you can stop accepting them in the first place. Enter greylisting.
These two articles are kind of follow-ons to my previous article on spam prevention in exim mail servers. Think of it as an appendix. If you are starting from scratch you might find is useful to go and read that first.
When most people install a free software mail transport agent (MTA) they plumb for Postfix, Exim, qmail or Sendmail. Whilst these are all fine, they can be a little over the top for some smaller systems or systems where all you need is some kind of local MTA functionality. In these cases many people will install their favourite MTA anyway -- but there are more lightweight alternatives. Here I look at one of them: Smail.
A few comments on my article The perfect network server in issue 17 requested some more in depth follow-up pieces. This is what I hope to be the first of those. It focuses on Exim, the mail transfer agent (MTA), specifically setting it up with spam scanning. It is based on setups I currently use, hosted on Debian GNU/Linux.