Anything that you'd use in an informal communication is inappropriate for a business letter. This includes slang, text_speak, emojis, and anything off_color or casual. If you're used to communicating mostly with friends, family, or even co_workers you've worked with for a long time, an appropriate closing for a business letter will probably feel pretty stilted at first. Don't worry about it – your colleague or business associate won't feel that way when he or she reads your correspondence. What seems unnatural to you will feel respectful and polite to the recipient.
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.