What's not as well known is the fact that merely
clicking on an email message just to delete it can let the spammer scum know that your address is valid.
Some of these dirtbags use what are known as "web bugs". It's an invisible graphic embedded in the email message which points to a CGI directory on their server. The URL of the graphic can have your email address in it or some code that represents your email address. When you open the email, the graphic tries to load, and your email program connects to their server, and quietly notifies them that you've read it.
If you can disable HTML in your email program, that's a good option. I use Netscape for my mail, and you can't disable HTML. Instead, I've gotten into the habit of temporarily disconnecting from the internet (by clicking the little "plug" icon in the lower left-hand corner of Netscape) while I go through new messages in my inbox. Once I've deleted any spam, I reconnect.
I don't know if it's because of this or something else, but my spam has slowly declined from an average of 25 per day to 2 or 3.
Here's some more info on web bugs:
Web Bug FAQ Check out the section about web bugs in email messages.
One filter that catches a great deal of spam is: Any Header does NOT contain MyName.