An Post is planning to close 161 post offices around the country.
The move is part of its transformation programme, and a €50m investment in the network.
It says 161 postmasters have applied for the company's voluntary retirement package.
A full list of post offices closing will be issued at the end of August.
The company says this is to confirm the details with each postmaster.
It says the company, the Irish Postmasters Union (IPU) and postmasters are "in agreement" that the consolidation of the network, and subsequent transfer of business to neighbouring offices, is "essential to the sustainability of the overall network".
Among the changes to the network are a lunchtime opening hours.
It adds that mail delivery and collection services are not affected.