An Post is offering everyone in the country a free digital stamp to mark its move to the EXO building on the north quays in Dublin city centre from the GPO in O'Connell Street.
The new An Post headquarters was officially opened by the Taoiseach.
An Post said its move marks the next phase of its business transformation and its digital development at the centre of the country's global ecommerce trade, logistics and financial services.
Six floors of the landmark EXO building will be occupied by 900 An Post employees, while over 180 employees will continue to work in a section of the GPO's office accommodation for another 18 months.
An Post said it will continue to maintain the GPO building and oversee its cultural programme until the building is transferred to the care of the OPW.
The EXO is the highest office building in Dublin and has been built to the highest standards of sustainability, certified as Platinum level Leadership in Energy and Environmental Design (LEED), NZEB - Nearly Zero Energy Building and has a BER rating of A3.
It has sustainable water, air-filtration and waste systems as well as multiple public transport links and provides bicycle parking for cyclists and charging facilities for electric vehicles.
Its eighth floor roof garden has living plant walls, native beach grasses and seating to encourage employees to take their breaks in the open air.
David McRedmond, the chief executive of An Post, said the company's "inspiring" new headquarters is designed for how the company works now and how its ways of working will evolve.
"Our new HQ will enable all our people to grow their skills and reach their full potential, guided by our commitment to Decent Work, diversity and equality. Our business partners, customers and the local community will be invited in to avail of our expertise and facilities," he added.
The free stamp is available to be downloaded on the An Post app.
The nine digit code can be used to post a letter anywhere within the country and ca be used immediately or within 31 days.
