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.
Do you need to write a business letter? Not sure about the best layout to use or what to include in your letter? It's important that all the business letters you write are properly formatted and professional in appearance. When you are writing to prospective employers, colleagues, professional and business connections, the layout of your letter is almost as important as what you are writing. If the letter isn't formatted correctly, doesn't have enough space between paragraphs, and uses a non_traditional font style or size, it can reflect poorly on you.