Regulations Governing the Handling of Mail Article 6
If the surface of a postcard is not smooth because of any glued attachment or projecting part, the postcard shall be enclosed in an envelope and posted as a letter.In the case of a piece of paper folded into something resembling a postcard, it shall be posted as a letter.
中文原文 郵件處理規則第6條
明信片因黏貼附件致表面欠缺平整光滑或有突出部分者，均應裝入封套內，按信函交寄。
紙張經折疊壓製，外形類似明信片者，按信函交寄。
紙張經折疊壓製，外形類似明信片者，按信函交寄。