Guy Kawasaki says every employee should unlearn this lesson after college

College can teach you a lot of important things, from how to conduct research to how to manage your time or learn a new subject quickly. It can be an important time of personal and professional growth.

But according to Guy Kawasaki, Silicon Valley venture capitalist and former Apple employee, there's one lesson most young people learn in college that they would be wise to forget.

It's the misguided idea, he says, that in order to communicate effectively, you need to use many words to fill page after page.

Guy Kawasaki
Source: Guy Kawasaki
Guy Kawasaki

"It seems to me that in education, a lot of things are about minimums — 10-page minimum, five-page minimum," Kawasaki told CNBC Make It at the Synergy Global Forum. "And then you go into business and it's a five-sentence maximum."

"It's this complete reversal," says Kawasaki, who launched his career in the tech world as Apple's former "chief evangelist" and today holds the same position at free graphic-design site Canva.

He says it's essential young employees learn how to be succinct in email, phone calls and conversations.

"I think you need to be able to craft a five-sentence email with a great subject line," he says. "I think you need to be able to leave a 10-second voicemail, to explain what you do in 30 seconds, to use five slides in PowerPoint."

"I think you need to be able to craft a five-sentence email with a great subject line." -Guy Kawasaki, chief evangelist at Canva

Research shows that managers prefer employees who can send clear, short emails or recap an idea briefly. Those exhaustive written responses or lengthy speeches you did for school? Your boss isn't going to find them helpful.

In fact, Julie Sweet, CEO of Accenture's North America business, says that the ability to write succinct emails is a skill bosses pay special attention to. To become a clearer communicator, she suggests jotting notes down before going to a meeting or writing a draft in a Word document before sending an email.

Bestselling management author and CNBC contributor Suzy Welch agrees that being clear in emails and in conversation will help you stand out.

"In business, writing long-winded things will impress no one, and irritate a lot of people," she says. "Get to the point as quickly as possible."

According to Kawasaki, succeeding in business "is about being able to communicate very succinctly, very effectively."

"Everything," he adds, "is brevity."

Check out CEO of a $16 billion business says the way you write emails can break your career.