could anyone please share basic rules of mailing in turkish. i mean such set phrases like english "dear sir", "sincerely yours" etc. i am interested in official correspondence.

thank you so much

-Dear sir/madam: Sayın ilgili kişi
-Dear Ahmet Çelik, etc : Sayın Ahmet Çelik / Sibel Demir,etc (state both name and surname)
-Yours faithfully, etc : saygılarımla

And is it common using "azızım'?

I think it is some old spoken, isnt it?