Estimates say that spam makes now up for 80 - 90% of all emails, and many mail servers have difficulties in managing the additional load caused by the latest spam, and spam filters such as SpamAssassin do not recognize large parts of that spam as they did before.

The biggest advantage if Citadel is ease of installation and ease of configuration. Both of these can be a serious hassle when you are building a Postfix mail server from scratch. So the focus of this documentation is clear easy configuration. The goal also requires a mail server that has an easy interface to make changes with and that is intuitive.

One of the best methods of restricting SPAM is to require address verification. This means that Postfix will initiate a SMTP session with the client’s server to verify that it is a legitimate address. This takes time and resources but…it a very effective way to deal with SPAM. You will need to add the reject_unverified_sender option.

"I run a Postfix-based mail server that services a few hundred users with an average load of a couple of thousand legitimate messages a day -- but thanks to spam, the actual load on the server is much higher. I use Realtime Blackhole Lists (RBL) and Distributed Checksum Clearinghouse (DCC) clients on Postfix and SpamAssassin to reduce the impact of spam."

I used to receive around 5,000-7,000 spams daily on angsuman [at] taragana [dot] com email which is publicly available on the internet. It was consuming too many productive hours daily to fight spam. I decided to fight back. To reduce the spams I first made changes to my postfix configuration with the aim to stop most spams upfront.

Although SMTP blocking of e-mail spam is a best practice, many anti-virus products include the dangerous option of blocking when a Received header is on a blacklist. But it is possible for a legitimate, secure system to have its e-mail blocked by this boneheaded technique. Do not use it!

The problem with vacation auto responders like 'vacation' for sendmail is that spammers often fake the From: address. Auto responding to these addresses can get your mail server blacklisted. To avoid this you can setup your autoresponder with procmail and, if you are running a spam filter on your machine, you can tell procmail to auto respond only if the X Spam Status header is 'No.'

One of the most frustrating problems with setting up any mail server is the configuration required for anti-virus protection and Spam checking. Amavisd-new provides an excellent tool to help in setting that up. This is a step-by-step process in providing your mail server, the example is Ubuntu 8.10, with the ability to scan all incoming mail for viruses and Spam.

Spam is a plague on the Internet. It’s constant and unending. Some ISPs and free web mail providers offer anti-spam services but if you’re running your own mail server, accepting mail to your own domain, you have to work out your own solution. Can open source compete with the big boys? When it comes to spam, is there a free lunch?