Commas with Salutations - Writing English
Use a comma if the sentence starts with an address to someone.
Example: Greg, can I talk to you for a second?
Use a comma with salutations in private letters.
Example: Dear Francis,
Don’t use a comma with salutations in business letters. Use a colon in American English and no punctuation mark in British English.
BE – Dear Mr Jefferson
AE – Dear Mr. Jefferson:
After the greeting, the comma is optional.