The "Mr.," "Mrs.," "Madam," and "Miss" are titles of courtesy and should not be omitted. The abbreviation "Esq." for Esquire is sometimes used; but the two titles Mr. and Esq. should never be used with one name, as "Mr. John Smith, Esq."
If a man is known by a military or other title, always use it, but never precede it with "Mr." nor follow it with "Esq."
Clergymen should always be addressed as "Rev.," the abbreviation for Reverend. If he is a doctor of divinity, add D.D. to the name, as "Rev. John Smith, D.D."
Medical doctors may be addressed as "Dr. John Smith," or "John
Smith, M.D."
THE GREETING
The greeting or salutation is a term of courtesy or esteem used in addressing the one to whom the letter is sent.
"Sir" is the formal greeting, and is used in addressing officials, or any strange male person. "Sirs," or "Gentlemen" may be used in the plural. "Dear Sir," or "My Dear Sir," is the usual form of greeting when a business letter is addressed to an individual.
Where the writer is acquainted with the person addressed, the usual form of greeting is "Dear Mr. Smith."
THE LETTER ITSELF
If writing in response to a letter received, the writer should begin in some such way as this: