Business letter format is basic and straightforward so that recipients can know where to find information. For example, in the business letter, the inside address is always below the date. However, matters become more complicated when there are multiple recipients for the letter. Letter writers often wonder if they should list all of the addresses on the inside address portion of the letter; the answer depends on how many addresses there are. Like so many formatting questions, you must use your best judgment.
Type your address, or use company letterhead.
Skip a line, and type the date.
Skip a line. If you have two recipients, type their names and addresses side by side or one on top of the other.
Make a decision if you have three or more recipients. Typing all of the addresses will make the letter look like a long list of addresses rather than a letter, so the best option is to simply omit the addresses to preserve the formatting and clean appearance of the letter. If you believe that omitting the addresses would cause offence, then you may decide to include them.
Address the letter by typing "Dear Mr./Ms. (Name), Mr./Ms. (Name) and Mr./Ms. (Name)" followed by a colon. Add as many names as you feel are necessary, but in the case of six or more recipients it is acceptable to simply address the letter to a committee or to name the group in some other way.
Write the rest of the letter as normal. Print the letters and mail them to their separate recipients.