Business letters are generally addressed to audiences external to a company (whereas memos are generally sent internally). Crucial to the success of the letter is a careful consideration of the audience and the purpose of the communication. While the letter itself is addressed to a specific person, the writer should keep in mind that the recipient may share the letter with others as well, who should be considered as secondary audiences.

In addition, business letters need to follow conventions of business writing, detailed in the links above.