in a formal letter which is first the salutation (sir..etc)
or the subject?
Please follow the link given below to study the proper format of formal letter:
https://www.meritnation.com/ask-answer/question/instead-of-showing-part-by-part-please-show-a-letter-for-sa/letter-writing/3453859
https://www.meritnation.com/ask-answer/question/instead-of-showing-part-by-part-please-show-a-letter-for-sa/letter-writing/3453859