The majority of emails, some 90-99 percent, sent through Yahoo's email system are spam, according to Jeff Bonforte, senior vice president of communications products at Yahoo Mail. In an interview with Tech Insider, Bonforte revealed that about 30 billion emails come through Yahoo's email system, and only a handful of those are actually delivered, the rest are rejected as spam. In fact, the company only delivers about 5 billion per weekday, and 2.5 billion on weekends.