Use a business closing and sign your name. Above all, be professional. If the you’re sending a physical letter, print it out and sign it by hand. Otherwise, just typing your name will do.
Use standard formal letter writing conventions to begin. A letter of recommendation is like any other professional communication, and follows the same general rules and guidelines. Place your address on the top right, followed by the date—spelled out. Below that, on the left, place the recipient’s name (if known) and address. Open the letter with a formal business greeting. Ex: Dear Ms. Smith, Dear Sir or Madam, (if you don’t know the recipient’s name)