Letter delivery will occur every second day in metropolitan areas, with some posties redeployed to process and deliver parcels.

No posties, or other directly affected employees, will be made redundant involuntarily during the period of the agreement, which expires in August next year.

There will also be no protected or unprotected industrial action during the period.

Australia Post chief executive Christine Holgate said the agreement would provide certainty as coronavirus impacts the business.

"No posties will be removed from the delivery service and we have been encouraged by the strong response from people wanting to move across to parcel delivery," she said on Tuesday.

She said the union also had acknowledged it was necessary to temporarily switch letter deliveries to every second day to safeguard the business.

CEPU communications union national president Shane Murphy said it was a win for workers on the front line of the pandemic.

"This agreement will ensure no posties are removed from the delivery employment mix - something we have fought hard for - protecting jobs and improving parcel delivery services to our communities," he said.

Staff working in processing and transporting mail under temporary delivery changes will also have their jobs protected.

Frontline workers will be paid a "thank you" bonus in recognition of the extra effort and risk during the pandemic.

Labor's industrial relations spokesman Tony Burke and communications spokeswoman Michelle Rowland said the government had capitulated one day before a Senate inquiry into the issue was due to start.

"While Labor welcomes today's victory, the fact remains mail delivery frequency to seven million Australian households is still being cut at a time when revenues are increasing," they said.

Finance Minister Mathias Cormann and Communications Minister Paul Fletcher said Labor cast uncertainty over jobs to score a political win.

"The agreement confirms the government's position that Labor was running a baseless scare campaign in the context of a by-election and spreading misinformation," they said.

Australian Associated Press