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.
Closing: When you're writing a business letter or email message it's important to close your letter in a professional manner, so you're letter, in its entirety, is well_written and professional. Signature: When you are sending a paper letter, finish the letter with your signature, handwritten, followed by your typed name. If this is an email, simply include your typed name. Finally, don't forget to spell check and proofread your letter before you send it. Again, ask a family member, friend or colleague to review it for you. It's always good for another pair of eyes to take a look because it's hard to catch our own mistakes.