When two or more men are addressed, do not omit the title Mr., before the name of each of the men, unless their names constitute a partnership or trading name.

Right: Jones & Smith, (firm name)
New York City.
Gentlemen:
Right: Mr. Jones and Mr. Smith, (not a firm name)
New York City.
Gentlemen:

Avoid all abbreviations of titles preceding the name except Mr., Mrs., Messrs., and Dr. Abbreviations of titles placed after the name, such as, Esq., D.D., A.M., etc., are proper.

Do not use Mr. and Esq. with the same name.

Avoid all other abbreviations except in case of a state with a very long name. In this case it is permissible to abbreviate, but it is better form to write the name in full. United States of America may be abbreviated to U. S. A.

Wrong: Merch. Mfg. Co.,
N. Y. C.
Gentlemen:
Right: The Merchants' Manufacturing Company.
New York City.
Gentlemen:
Wrong: Mr. William Shipp,
Bangor, Me.
Dear Sir:
Right: Mr. William Shipp,
Bangor, Maine.
Dear Sir:

Do not place a period after the title Miss. Miss is not an abbreviation.

The Salutation