sendmail Cookbook

Chapter 6. Controlling Spam

Introduction

Spam mail: you know it when you see it, and everyone has seen the ridiculous advertisements for investment schemes, pornography, herbal cures, and everything else imaginable. Many experts categorize all Unsolicited Commercial Email (UCE) as spam, and certainly UCE clutters electronic mailboxes around the world. However, legitimate advertisers who offer real “opt-out” schemes are not the worst problem.^[1] The real problems come from spammers. What distinguishes spammers from legitimate advertisers is that spammers hide their identity and abuse other people’s systems. These traits can be seen by the fact that:

• Spammers hide the origin of the email so that no one knows they sent it. Legitimate advertisers proudly display their company name in the sender address. Any advertiser who doesn’t probably has a reason to hide who they are and what they are doing and should be considered a spammer.

• Spammers abuse the services of other people’s systems by using those systems as unauthorized relays.

• Spammers send information you never asked to receive. You don’t join a spammers’ mailing list, and when spammers provide an opt-out scheme, it does not opt the user out of anything. Instead, the scheme is used to collect email addresses to sell to other spammers.

You must do your part to reduce spam for everyone by ensuring that your system is not misused by remote spammers and that your local users do not contribute to spam.

Spammers use open mail relays to hide ...