How do you know for sure whether or not to use a closing? One good test is to ask yourself whether this email is more akin to an instant message/text or a business letter. If you're giving your teammate a quick update on an ongoing project, a formal closing might not be necessary; if you're throwing your hat in the ring for a promotion, it definitely is required. When all else fails, and you're still not sure, err on the side of caution and include it. You'll never go wrong by being too polite and respectful.
Business Letter Format: Review a formatted business letter with information on what to include in each section of your letter. When you are writing a business letter, it's important to include an appropriate salutation at the beginning. This is true whether you send your message via email or through the mail. Using an appropriate greeting sets the tone for your letter and shows the recipient that you understand basic rules of business etiquette.