What is the correct punctuation after the salutation of a letter--a colon, semicolon, or comma?
Either a colon or a comma may be used, depending upon the degree of formality desired.
A colon follows the salutation in formal letters:
Dear Ms. Gregorson: Members of the Board:
A comma follows the salutation in informal letters:
Dear John, Edward,
The use of a semicolon after a salutation is improper.