original: Postal systems often have functions other than sending letters.
simplifications: Postal systems often do more than just send letters. Postal systems provide more services than sending letters. Postal systems often do more than send letters. Postal systems often do things other than sending letters Postal systems can do more than just send letters. Postal systems have functions other than sending letters. Postal systems often have tasks besides sending letters. Postal systems have other functions than just sending letters. Postal systems do other things other than just sending letters. Postal systems do more than just send letters.