The No. 1 mistake people make when writing work emails

The average office worker spends six hours a day checking email, receives about 121 of them daily and hoards an average of 500 unread messages.

How do you make sure your manager or peers not only notice your emails, but actually read them? Two career experts share the number one mistake people make when writing work emails: typing ones that are too long.

Workplace strategy expert and author of "The Healthy Workplace" Leigh Stringer tells CNBC that email is most useful in a transactional sense, such as sending documents and attachments or setting up meetings and deadlines. "A long email is a signal you're using the wrong communication tool," says Stringer.

Referring to the 1950s research of Albert Mehrabian, who postulated that over 90 percent of communication is done through body language, Stringer says a lot of information is lost when trying to convey big ideas over email.

"It's the twinkle in our eye, it's the little nudge that we give each other. There's so much in face-to-face and even telephonic communication that provides so much more data rich information," Stringer says. "In email, often we're trying to make up for that."

Here are three problems with sending long work emails and the solutions to fixing them:

For Dan Schawbel, a millennial career and workplace expert, part of the mistake of writing long emails is treating everyone at work like your friend, "instead of knowing your audience and then shaping your language, the length and the tone of the email to that individual."

"If you're going to write your manager or a team member an email," Schawbel says, "it can probably be more casual because you know them and they know what to expect of you."

The solution: "To someone you don't know in the organization, especially an executive, it needs to be much more formal," he says. "You need to tighten up your language, make it more concise and be straightforward instead of trying to tell jokes or using emoticons."

"Technology in the workplace has made everything so convenient," Schawbel says, highlighting how email and instant messaging notifications provide a false sense of gratification. "But you can accomplish more through short in-person meetings," he says, adding video chats are the next best thing for telecommuters.

"If it's an open-ended question, an in-depth question or a complex question that requires back and forth banter, it's probably worth a phone call," Stringer says. "You think it's faster communicating over email but it can actually be a time suck."

The solution: Pointing out how people have lost the attention span for content longer than 500 words, Stringer recommends keeping emails much shorter. Consider using bullet points, highlight or bolding words that specifies where an action is necessary, or using a maximum of two paragraphs, she says.

Employees need to recognize people don't have the time to read through long emails, Stringer says: "You never know what your boss is going through, don't assume you are the only person in your boss' life."

The solution: Shorter emails also show respect for the other person's time. "Quick notes on the status of a project you're working on and keeping your boss informed is a good habit to form," Stringer says, "but a bad habit would be to try to fit everything into one long email that might have a negative tone to it."

Stringer says employees should be flexible, positive, patient and should air on the compassionate side. "A long email email that hasn't been edited for tone will come across significantly more negative than you meant to, she adds. "Sometimes there's no amount of emoticons that make up for language that appears negative."

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