Writing a business letter to someone you don't know is typically no more difficult than writing a letter to someone you're already acquainted with. The format of the letter, however, should still be professional and adhere to proper standards of communication etiquette in business. Before beginning a business letter, make sure you know how to spell the recipient's name correctly and have the person's correct title and company address.
Start the letter with a proper business introduction for an unknown person, such as "Dear Mr. Smith" or "Dear Ms. Johnson," using the person's own last name. If the letter is addressed to a female whose marital status is unknown, use the prefix "Ms." End the introduction with a colon instead of a comma if the letter is more formal in nature.
Introduce yourself to the recipient since you haven't yet met. Explain why you are writing in the first paragraph of the letter. Convey in a professional voice the purpose of your inquiry and what it is you're asking of the recipient.
Type the letter in a business appropriate format. Use paragraphs that are flushed left to the side of the page and avoid paragraph indentations. Include a single space after each paragraph. End the letter with a business-appropriate signature such as "Sincerely" or "Best Regards."
Use a professional and objective voice in the body of the letter. Remain unbiased and friendly while still conveying respect. Include a note of thanks for his time.