In the UK, the convention is : a) If you know the name: "Dear Mr / Ms / Mrs [Family Name]" b) If you don't know who it is : "Dear Sir / Madam" c) If you know that it is a man but not his name : "Dear Sir" d) If you know that it is a woman but not her name : "Dear Madam" You would write the title e.g. "Accounts Manager" in the address or you could write below the address, for example: "For the Attention of the Accounts Manager". You would only write "Dear Sirs" if you were addressing the company in general and not addressing a specific person. You would never write "To Whom it May Concern" in this kind of letter. It's possible that US conventions differ slightly.

If you address someone , you normally use HIS NAME or HIS GENDER , not his position in a company . Dear Sir / Dear Sirs ( for male > " Sirs" is very formal) Dear Madam ( for female) . To whom it may concern or Dear Sir or Madam ( When you do not know the gender) Dear Ms. Sally ( use this if you do not want to state her status as a married women or you don't know if she is or not) Dear Mrs Sally ( you stated her married status)