party by post

You are my fave author, Melanie, mailed this 'party' pinåta (sans box!) to her nieces and nephews. It's an awesome idea, however, I've got so many questions. Did she just pop this in the mailbox? Or did her post office really let her mail the hat? If so, how did they affix postage? Isn't silly string considered an explosive of some kind since it is combustible? I can't imagine the guys at my P.O. allowing me to send this in the mail, but now I feel I should at least try.