The postal counties of the United Kingdom, now known officially as the former postal counties, were postal subdivisions in routine use by Royal Mail until 1996. The raison d'être of the postal county – as opposed to any other kind of county – was to aid the sorting of mail by enabling differentiation between like-sounding post towns. Since 1996 this has been done by using the outward code (first half) of the postcode instead. For operational reasons the former postal counties, although broadly based on the counties of the United Kingdom, did not match up to their boundaries, in some cases with significant differences. The boundaries changed over time as post towns were created or amended.