also: ふっけい
noun
Dear Sir or Madam, in reply to your letter ...
Formal salutation used at the beginning of a reply letter, corresponding to 'Dear Sir or Madam, in reply to your letter ...' in English. Used in traditional Japanese correspondence.
拝啓、春暖の候、貴社ますますご清栄のこととお喜び申し上げます。復啓、先日はご丁寧なお手紙をいただき、誠にありがとうございました。
Dear Sir, I hope your company is thriving in this spring weather. In reply to your kind letter the other day, thank you very much.
From 復 (ふく, 'reply') + 啓 (けい, 'to open, to state'). A set phrase in traditional letter writing.