Two years ago, hardly anyone in Australia's business community had even heard of Dave Greiner and Ben Richardson. Today, despite having founded one of Australia's most valuable start-ups – arguably the most exciting technology firm this nation has produced to date – they are still relatively unknown figures.

Campaign Monitor, the email marketing firm they founded in a garage in Sydney's Sutherland Shire over a decade ago, shot to prominence in 2014 when Greiner and Richardson sold a $US250 million ($348 million) stake in their business to prominent US venture capital firms. It remains one of the largest investments into an Australian tech start-up.

Yet Richardson and Greiner are not household names and have rarely given media interviews "Yes, it's a conscious thing," says Richardson tells the Australian Financial Review. "The two of us have no particular interest in building a profile or pushing a political agenda."

This week, the AFR Magazine tells the story of Campaign Monitor's remarkable rise from obscurity to global prominence. Greiner and Richardson, who don't work on Mondays and for years listed their own credit cards on the company's intranet for staff to use for expenses, now have an estimated combined wealth of $543 million, ranking them in 118-119th place in the BRW Rich 200.