Used colloquially and incorrectly today by young people as a sarcastic and dismissive method of dismissing someone else's criticism -- often to have the last word.
Mature person, "I prefer to watch classic horror films because they relied on well developed storylines and good storytelling principles instead of today's CGI horror films"
Teenager, "duly noted."
An expression used in an email response when you're blowing someone off who is on a tangent that isn't worth responding to. There isn't much they can send back after this type of response.