It's a hard job but a good job, particularly as it keeps the women fit for their sporting commitments. When all three employees of the Papakura branch were selected for the Kiwi Ferns team to play a three-test series against Australia's Jillaroos at the Nines - a commitment that would require them to be off work for the best part of the week at the same time - it seemed they would be forced to choose between their jobs and their dreams. Their leave applications were declined and they considered quitting.
"There was pressure on us to make that choice," says Mariu, a 15-year veteran of the national team. Happily it didn't come to that after postal staff were brought in from other branches to cover their absences.
Still, it hasn't been easy. Training for the tournament ran from 10am-4pm on Saturdays, so the women had no option but to begin their four-to-five-hour delivery rounds early.
"We were quite buggered then," admits Hilda Peters.
It's not like they aren't used to it. Posties work six-day weeks, every week. And in women's league Sunday is match day.
"Our rest day is game day, basically," says Mariu.
It's all a far cry from the world of the professionals from the NRL who get paid to train and play while not needing to hold down a day job.
Added to this year's schedule as a way of creating longer breaks between the NRL games - particularly during Sunday's finals programme - the women's matches should be fiercely contested.
The Kiwi Ferns have traditionally held the upper hand in the transtasman rivalry, winning the first three world cups between 2000 and 2008. Australia has begun to take the women's game more seriously, with the Australian Rugby League throwing considerable resources behind the Jillaroos. That paid off with a world cup final win over the Kiwis in England in 2013. The Ferns took their revenge with a 12-8 victory in a curtain-raiser for the Kangaroos versus Samoa Four Nations test in Wollongong in November, but even then the playing field wasn't level.
While the Kiwi women had to partially fund the trip out of their own pockets, their Aussie counterparts received $500 match payments.
But it's not about money. This weekend represents a rare chance for the women's game to showcase itself.
"It's more exposure for women's rugby league in general, that's the biggest thing," says Kahurangi Peters.
As the hype around the tournament builds, so too are the nerves in the Kiwi Ferns camp.
"You hear it on the radio and it is like 'oh my God I am going to be in that'," says Hilda Peters.
But unlike their superstar male counterparts in the NRL, reality awaits the women at the final whistle. Come Monday morning the mail will still need to go through, and Papakura's star posties will be there to deliver it.
Kiwi Ferns v Jillaroos
• Three-test women's international series added to the Dick Smith NRL Auckland Nines programme for 2015
• First match is Saturday at 4.00pm
• Matches two and three Sunday following the completion of the quarter-finals (4.35pm) and semifinals (6.40pm)
• All three games to be televised live by SKY TV.