Capital Letters in Address Field (Family name)?

Is it acceptable when writing a formal English letter to write the Surname of the person addressed in capital letters, or is the first and last name to be written in the same size letters, ie. Mr Peter SMITH or Mr Peter Smith. Which one is correct? I am posting this question because at work we also write many French formal letters. In French it is quite common to write the last name in capital letters. Would that be permissable in English as well or is this conisdered "bad" style?

thank you and
kind regards
SF

[bhaisahab]

It's more usual to write 'Mr. Peter Smith' rather than 'Mr. SMITH, Peter' in the French way.