In general use, “SPAM®" is a brand name of luncheon meat and is a registered trademark of Hormel Foods Corporation. After SPAM® was lampooned by Monty Python in a famous sketch, it was jokingly adopted by the Internet community to describe unsolicited mass postings across many USENET groups. Soon, a new word was coined, the lowercase “spam,” a word that now describes unsolicited, commercial email.
As you read this chapter, remember that spam is a moving target. On the one hand, sendmail offers constantly improving tools to filter and reject it. On the other hand, the spammer’s tools are constantly being updated to bypass existing protections. Mix in the fact that laws are being written which might modify or limit spam, and you can think of this as an arms race. That is, you won’t set up sendmail just once and be done, but will find yourself continually modifying database files and rule sets in an effort to stay even with the spammer’s cleverness.