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Dear (so and so); Dear Sir; Dear Madam; To Whom It May Concern
手紙の冒頭に拝啓と書くのが日本の礼儀だ。
Writing a formal greeting at the start of a letter is Japanese etiquette.
正式な手紙の書き出しは拝啓で始めるのが一般的だ。
I began the letter with 'Dear Sir'.
拝啓、時下ますますご清栄のことと存じます。
Dear Sir or Madam, I trust you are well and prospering.