It is almost always a comma, but rarely I have seen a colon. When you are writing a formal letter, it is a comma, but if you were to write a informal letter to a friend, it doesn't really matter. For all of the letters I write I use a comma, and so does everybody else I know.
Colon
comma
Note
Using a colon in the salutation and a comma in closing.
A comma is not required in the salutation of an editorial letter. You can use either a comma or a colon after the recipient's name. For example, "Dear Editor," or "Dear Editor:".
A comma is typically used at the end of a salutation in both formal and informal communication. For example, "Dear John," or "Hi Mary,".
Mixed punctuation is a style of formatting business letters where a colon is used after the salutation and a comma is used after the closing. This formatting style is less common today and has generally been replaced by open punctuation, where no punctuation is used after the salutation or closing.
No. A comma follows the complimentary close when mixed punctuation is used (meaning a colon was used after the salutation)
comma or colon Examples: Dear A n na, Dear Sirs:
A comma should follow the closing if there is a colon following the salutation.
a comma, unless you write "To whomt it may concern", then you should put a colon (:)
A salutation ends with a colon when it is used in a formal or business letter or email. It is commonly used before the body of the message, such as "Dear Mr. Smith:".