In June last year, Murray and Liz Bell, from Whitestone Taxis, launched Whitestone Post, which guarantees 24-hour mail delivery within the town's boundary.
The registered postal service was set up to fill a gap in local mail services, initially targeting the business community.
While the original intention was to deliver local mail overnight to provide some financial relief for their taxi business, a much greater opportunity has emerged.
As well as local delivery, it has developed into an exclusive agreement with New Zealand Post, which delivers any Whitestone Post mail outside the district.
Now, Mr Bell believes the model could be duplicated New Zealand-wide and the couple hope to replicate it in other centres around the country, branded as Whitestone Post.
Talks with other taxi companies showed they were ''very, very keen'' to look at the proposal.
It was Dunedin-based business coach Carl Spruyt who suggested Mr and Mrs Bell look ''outside the box'' for additional quiet-time work.
Any profits the taxi business made during the busy times were being eroded by the quiet times and the question was what to do about it.
He proposed the couple investigate delivering mail for local businesses, offering the guarantee of overnight delivery.
While Mr Bell was unsure at first, but once he found the volume of mail involved, he realised the income was quite significant.
The only real costs were running costs for vehicles that would otherwise be sitting idle.
Whitestone Post produced its own stamps and prepaid envelopes, providing an income stream before mail was even delivered.
Locally, mail was delivered overnight five days a week, at 70c an item. Since launching last year, Whitestone Post had delivered close to 80,000 letters.
By paying 70c instead of New Zealand Post's 80c, local businesses were saving a total of $8000.
Demand was there and it was increasing. Businesses were finding it expedient to send out accounts weekly, meaning faster payment, Mr Bell said.
The company was able to manage the growth because it had vehicles and staff at the ready at night-time, so it suited a taxi business.
Clients included accountants, real estate companies, garages, doctors, dentists, beauty salons and others needing to send direct mail, accounts or notifications of appointments.
Whitestone Post now had a franking machine that put a barcode on envelopes, which New Zealand Post recognised ''and delivers anywhere we can't deliver''.
That was mainly New Zealand-wide, but mail could be sent anywhere in the world in a Whitestone-branded envelope.
''It's really exciting. It's grown way beyond what we'd even hoped,'' Mr Bell said.
While any contractor would be able to set up to provide the delivery service, taxi firms were a logical choice.
They had the vehicle ''dead time'' during the night, so there was no need to buy any additional vehicles and taxi firm staff knew their areas well.
New Zealand Post had been ''incredibly supportive''.
''I think they can see it as a solution for what they are struggling with,'' he said.
Challenges remained in the taxi industry.
The fall in patronage was still real, particularly with the drop-off in the hospitality industry and, had they not changed their business model, the couple would have been struggling.
He was grateful for the encouragement of Mr Spruyt, who had been ''brilliant'' for their business.
''Lots of businesses would benefit from having a Carl to give them an outside view,'' Mr Bell said.
When they first saw him three years ago, they were ''pretty much ready to walk away'' from the business, he said.
