An Post says Dublin has become the first capital city in the world to see zero emissions postal delivery.
The postal service has eliminated carbon emissions in the immediate city centre by introducing electric trucks.
It is proposing a 100% 'Green Delivery Zone' in Dublin, with a zero emissions policy being extended to all cities by the end of 2020.
An Post says the 47 zero emission electric trucks have been added to its existing electric fleet.
These trucks have avoided 450 tonnes of CO2, benefitting the health and air quality of 512,000 people living and working in the city.
Zero carbon emission delivery will be rolled out to Cork, Galway, Kilkenny, Limerick and Waterford by the end of 2020.
The company says its electric fleet will exceed 900 within two years.
An Post CEO David McRedmond says: "We've proven that zero carbon emission delivery in a capital city is achievable.
"If An Post can do this, delivering to more than 70,000 premises daily in this area, there is no reason why other companies can't.
"Let's aim for a 100% Green Delivery Zone in Dublin."
Kate Ruddock, deputy director of Friends of the Earth, adds: "We commend An Post for leading the way to become the first postal service in the world to attain zero carbon emission delivery status in a capital city.
"We also commend An Post for rolling-out their green delivery zone to other major cities and towns across Ireland whilst calling on other organisations to do the same benefitting the health and air quality of the country."
Since 2009, An Post says it has focused on reducing property energy consumption by 23% and its carbon foot print by 35%.
It is also installing solar energy in larger offices.
Late last year, the company received a €40m loan from the European Investment Bank (EIB) to drive its digital, retail and green transformation.