"His Grace the Duke of Fife" is the form of address for a Duke; "My Lord Duke" being the salutation, and "Your Grace's most obedient servant" the subscription.
In writing to the Pope of the Roman Catholic Church, one should address the letter to "His Holiness, Pope ——, Rome." The salutation should be "Your Holiness," but the conclusion remains the same form as for other dignitaries. A Cardinal of the same church is addressed "To His Eminence (Christian name) Cardinal (surname)," and greeted as "Your Eminence." Formality should be strictly observed.
An Archbishop of the Church of England is addressed, "The Most Reverend (name) His Grace the Lord Archbishop of (name of bishopric)." The salutation is "My Lord Archbishop;" the subscription, "I have the honor to be, with the highest respect, Your Grace's most humble servant." A Bishop is addressed "The Right Reverend the Lord Bishop of (name of diocese)." He is saluted "My Lord Bishop."
In the United States the Bishops of the Protestant Episcopal Church, who are not here Lords, are addressed, singly, as "The Right Reverend (Christian name and surname). D. D.," or "The Right Reverend Bishop of (name of diocese)." They are saluted, singly, "Most Reverend Sir."
The word "To" may precede a formal or ceremonious address, adding to the formality.
An envelope containing a letter or card of introduction should never be sealed, if presented in person by the party introduced. If, however, he should deliver it by messenger,—an exceptional procedure, and one not to be followed by a man except in unusual circumstances,—the envelope may be sealed.
No letter sent through the kindness of a friend should ever be sealed. The envelope should bear, in the lower left-hand corner, the acknowledgment of the favor in words like "Kindness of Miss Hallowell."
Salutation, Conclusion, and Signature of Letters
A stranger should be saluted as follows: "Mr. Eugene Motley, My dear Sir;" "Mrs. Alonzo Parmenter, Dear Madam;" or "Eugene Motley, Esq., My dear Sir." These are forms slightly more formal than "My dear Mr. Motley," or "My dear Mrs. Parmenter," which in America are strangely considered more formal than "Dear Mr. Motley," or "Dear Mrs. Parmenter," although in England the reverse is true. Therefore, a mere acquaintance is addressed "My dear Mrs. Judson," while a friend is addressed "Dear Mr. Clark."
A married woman signs her name, as "Ethel Husted," and then puts her formal name, "Mrs. Hollis Husted," in brackets a little to the left of and a little below the other.