The first spam e-mail was sent on May 3, 1978, by Gary Thuerk, a marketing guy for DEC. He tried to send it to about 400 people on the modern Internet's predecessor, ARPANET, but due to design limitations the first wave reached only about 320 people--a little more than 10 percent of the total user base at the time. What's more, it was written in all caps.

You can read the message (along with several indignant replies) here.