An interesting blog about couriers and courier services in Australia:

http://courier-quotes.posterous.com/information-about-couriers-in-australia

A courier is a someone or a company employed to deliver shipments, boxes, satchels, messages, packages and mail. Couriers are distinguished from ordinary mail services by features such as speed, security, tracking, signature, specialization and individualization of services, and committed delivery times, which are optional for most everyday mail services. It is a common misconception that couriers are more expensive than mail services there is always a breakpoint or threshold where a door to door courier service is a) Cheaper b) Easier ! However there are certain service levels consumers can select from hence offering a premium courier service, couriers  than usual mail services, and their use is typically restricted to packages where one or more of these features are considered important enough to warrant the cost.Different courier services operate on all scales, from within specific towns or cities, to regional, national and global services.