First (for reference):
I know I can also use "Best regards" or similar endings, but I just want to know out of curiosity. I know THAT
, [no comma] when I 'm writE ing "Dear Mr Sesambroetchen,[comma]" that I 'm usE ing "Yours sincerely" and when I 'm writE ing "Dear Sir or Madam," I 'm writE ing "Yours faithfully," [comma] but what if I'm writing "Dear colleagues"? It's not a NAMED direct person but it is ALSO not AN that unknown as "Dear Sir or Madam". I hope , [no comma] you understand my doubt.
As to which option you need, it depends on the nature of your relationship with your colleagues. It might not matter very much--though I would definitely avoid anything with "[S.O. B.]" (-;
I might well use "(Best) (R)egards."
So far as I'm aware, "Yours faithfully" has been old-fashioned for some decades now.