Hotmail (Internet, software): A free Web-based e-mail service now owned by Microsoft Corporation. A fine example of viral marketing. It grew its subscriber base from zero to 12 million users in only 18 months - faster than any other company in any industry in history, and with a budget of only $50,000. It did so by including "P.S. I love you. Get your free email at" at the bottom of every email sent. Later it was changed to be less endorsing by removing "P.S. I love you." Hotmail became the largest e-mail provider countries like Sweden and India, without any marketing there.

Today there are many Hotmail clones but it is still popular as a free e-mail provider.