The research also found workers in their 60s were the least guilty, with 68 per cent of employees in this age bracket never having mail sent to the office.
CouriersPlease CEO Mark McGinley said online shopping was now a fact of life for most full time employees.
"With the latest statistics showing Australians spent $24 billion online in the 12 months to November 2017, and with online retail sales increasing by 4.7 per cent in November last year — the highest monthly growth rate since 2014 — it's clear that online shopping is a fact of life for the majority of Australians," he said.
"While most workplaces recognise this, there are still numerous workplaces that need to adapt to the pervasiveness of online shopping in Australia.
"The retail industry is reliant on smooth parcel delivery options to continue accommodating growing customer demand for online goods."
Mr McGinley urged workers to check their office's parcel delivery policy and to discuss the issue with a manager if the rules were unclear.
If personal mail delivery is banned altogether, he recommended redirecting mail to a secure parcel locker or retail outlet to ensure it arrived safely.
Failing that, having the item delivered to a trusted neighbour was another option.