"Even if one million motorists decided to use the highways without e-tags every day, and we received one million e-toll bills per day, our systems would be able to handle it," said Newyear Ntuli, group head of e-business at Sapo.
He said the SA Post Office already handled an average of 450 000 traffic-related post per month.
Last week, Transport Minister Dipuo Peters announced that e-tolling in Gauteng would begin on December 3.
Road users without an e-toll account, or a day pass, have a seven-day grace period to pay from the time he or she passed the gantry.
A bill would be sent through the post if the account is not paid within seven days.