All letters and notes, with a few special exceptions, require a prompt acknowledgment of receipt, if not an immediate answer.
This is especially the case in business letters and those containing enclosures of any kind.
All letters and notes should be courteous. To inferiors in station be kindly; to superiors, respectful; and to equals, friendly.
All letters and notes asking information should be re-read immediately before answering.
OFFICIAL AND TITLED SALUTATIONS
Titles in the United States are either official or academic.
OFFICIAL TITLES
To the President of the United States, an official letter commences, Sir.
Conclusion: I have the honor to remain your most obedient servant.