The standard business format consists of a header, inside address, subject line, greeting and block format for the text. (work.chron.com)
The letter should also be professional in appearance, and be written in business format and edited well. (thebalance.com)
• Use the professional business format: Although effective cover letters are personable, the cover letter is technically a formal document and must be treated as nothing less. (eresumecoverletter.com)