Earthlink was responsible for a lot of this stuff. I haven't seen one of these messages in ages, so perhaps the company finally wised up and stopped using this scheme. If your email service offers it by default as a way to protect you from spam, disable it and find another way, or switch to a different service.
Be a spammer yourself: Finally, consider the golden rule. If you don't like receiving unsolicited email, there's a very good chance that others don't either. You may have the most adorable cat on earth, believe fervently in a political or religious cause, have the greatest business plan ever devised, or have faith that good luck comes in the form of chain mail, but sharing this stuff with everyone in your address book makes you the spammer. You absolutely want to spread the word to people who have indicated their willingness to listen, but be sure you have very strong evidence that this willingness exists. Ask, rather than assume, and your email life will be far more harmonious.
Sign up for Computerworld eNewsletters.