Define open letter puctuation?

Answer 1

I don't know but I trust you will tell us once you find out.

Answer 2

As far as punctuation after the salutation and closing is concerned, the standard is to use a colon after the salutation (never a comma) and a comma after the closing. There is also a less accepted format, known as open punctuation, in which punctuation is excluded after the salutation and the closing.