Back in 1916 Post Boxes [Pillar Boxes] in Dublin would have been painted red rather than green as they are today so someone came up with the idea of painting selected Pillar Boxes red to recreate the Dublin of 1916 but unfortunately they selected some P&T post boxes which would never have been painted red. I do not know if the other pillar boxes are P&T boxes but I do know that many people are not at all happy with the idea but I do think that the idea was not at all bad.

It should be noted that originally all post boxes across Ireland and the UK were green, before the British post office switched to red in the 1880s.

Following Irish independence in 1922, existing British pillar boxes were retained, and simply painted green. Many of these are extant around the country, retaining the monogram of the monarch who reigned at the time of the box's installation. The Department of Posts and Telegraphs continued installing similar pillar boxes and wall boxes, but with the initials SÉ (for Saorstát Éireann), a harp or the P&T logo, instead of a monarch's monogram. Since 1984 An Post, the current Irish postal administration, uses the An Post logo to adorn its posting boxes.

A post box (British English and others, also written postbox; known in the United States and Canada as collection box, mailbox, letter box, or drop box) is a physical box into which members of the public can deposit outgoing mail intended for collection by the agents of a country's postal service. The term post box can also refer to a private letter box for incoming mail.

A pillar box is a type of free-standing post box. They are found in the United Kingdom and in most former nations of the British Empire, members of the Commonwealth of Nations and British overseas territories, such as Australia, Cyprus, India, Gibraltar, Hong Kong, the Republic of Ireland, Malta, New Zealand and Sri Lanka. Pillar boxes were provided in territories administered by the United Kingdom, such as Mandatory Palestine, and territories with Agency postal services provided by the British Post Office such as Bahrain, Dubai, Kuwait and Morocco. The United Kingdom also exported pillar boxes to countries that ran their own postal services, such as Argentina, Portugal and Uruguay.

Mail is deposited in pillar boxes to be collected by the Royal Mail [UK], An Post [Republic Of Ireland] or the appropriate postal operator and forwarded to the addressee. The boxes have been in use since 1852, just twelve years after the introduction of the first adhesive postage stamps (Penny Black) and uniform penny post.

Mail may also be deposited in lamp boxes or wall boxes that serve the same purpose as pillar boxes but are attached to a post or set into a wall. According to the Letter Box Study Group, there are more than 150 recognised designs and varieties of pillar boxes and wall boxes, not all of which have known surviving examples. The red post box is regarded as a British cultural icon. Royal Mail estimates there are over 100,000 post boxes in the United Kingdom.