A little background…
During the 2004 World Economic Forum in Switzerland, Bill Gates -- then chief software architect of Microsoft -- predicted the end of email spam within two years through several potential means.
Two of the ideas involved solving puzzles while a third, and the most promising according to Gates, would have allowed email recipients to charge the sender a small fee akin to postage stamps, or waive the fee for family and friends. "In the long run, the monetary (method) will be dominant," he predicted.
Despite Gates foreseeing a spam-free world by 2006, 2007 brought a record level of unwanted emails, with spam messages totaling 10.8 trillion for the year compared to 10.5 trillion legit ones. Thanks in part to better filtering, however, the percentage of spam to legit emails has gradually improved starting around 2008 with about 54% of the total email traffic being spam, according to Statista.