For business customers, a new priority mail service would also be available in and between Auckland, Wellington and Christchurch.
"New Zealand Post will continue to seek ways to improve efficiency and make cost savings to maintain a commercially viable postal network, and to give our customers the best possible service."
The union for NZ Post workers, E tū, called the move "the end of an era for postal services" that could result in job losses.
"Post's decision to wind up its Fast Post service signals the end of an era, but also reflects the reality of today's postal services."
Industry coordinator Joe Gallagher said NZ Post had indicated that it intended to redeploy posties who risked losing their jobs into other roles, as business ""booms" for the organisation's parcels and logistics business and its courier service.
"That's where the business is moving," he said.
"Fast Post business dropped by 23 percent over the past year. On the other hand, demand has surged for parcel deliveries for customers such as The Warehouse, My Food Bag and Amazon.
"While this means change for many of our 500 postie members, there will be opportunities within the delivery area at NZ Post."
The union intened to work to ensure NZ Post absorbed job loseeses into other areas.
"We want to protect full-time, good quality jobs and to keep the vital link which posties provide to the community," Gallagher said.
FastPost cost between $2.30 and $4.30 depending on the size and weight of the package.