We’ve all done it: typed out an email or handwritten a note, signed it and then remembered something important we forgot to say. That’s when we turn to those two familiar letters at the end, P.S. But ...

Letter writing has been an art form for many centuries. From "x" and "o" meaning "hugs and kisses," respectively, to the intricacies of deciding what salutation to use in a letter, it may take some ...