The postal counties of the United Kingdom, now known as former postal counties, were postal subdivisions in routine use by the Royal Mail until 1996. The purpose of the postal county – as opposed to any other kind of county – was to aid the sorting of mail by differentiating between similar post towns. Since 1996 this has been done by using the outward code 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 with their boundaries; in some cases there were significant differences. The boundaries changed over time as post towns were created or amended.