Example of social letter and business letter?

Social letters are different from business letters. Social letters are like friendly talks and include an easy conversational style. For example: Dear friend, I have been thinking of you lately. The letter can end with Sincerely and include your name. A business letter is formal and should have a professional tone. For example: Dear Mr./Ms. I am taking the time to inquire about the job, etc. The ending should include: Thank you or Best.