Salvation Army gets the stamp of approval
But as the postal service's chief executive Christine Holgate explains, there is much to bind them.
"We are two of the nation's oldest organisations, we are in the very fabric of the communities of Australia," she said.
"We are here to serve the people."
Australia Post has issued a stamp celebrating 125 years since the Salvos took over the building at 69 Bourke St as their headquarters.
Originally owned by the YMCA, the building is steeped in history - one of the world's earliest movies was filmed there, and many luminaries have spoken there including federation activist and former prime minister Alfred Deakin.
Today, 69 Bourke St is best known as a refuge for the homeless, with its Night Cafe hosting at least 150 vulnerable Melburnians each night.
Australia Post provides volunteers for the cafe and it recently installed lockers and post office boxes for the homeless.
Major Brendan Nottle, who runs the Salvos Project 614 on the site, said the new facilities gave dignity and respect to the downtrodden.
"Australia Post don't help us from a distance, they come in and help in a practical way so we're able to run services to some of the most vulnerable people in the city," he said.
Ms Holgate will be among 160 prominent and not so prominent Victorians who will attend the Salvos 125th celebration dinner at Bourke St on Friday.
Other attendees include Lord Mayor Sally Capp and Victoria Police Chief Commissioner Graham Ashton.