Four letterboxes were painted black to honor black Britons, including Sir Lenny Henry and nursing pioneer Mary Seacole.
The Royal Mail letterboxes – in London, Glasgow, Cardiff and Belfast – were painted as part of Black History Month in October.
Each features an important figure in the British black community and has a link to social media.
Royal Mail says the aim is to help mark the success of black Britons.
A QR code on letterboxes can also be scanned to reveal a list of black Britons who have appeared on special stamps.
The London Mailbox is in Acre Lane, Brixton, near the Black Cultural Archives.
It features the ‘Queuing at the RA’ image of Yinka Shonibare, one of six artists who have been commissioned by Royal Mail to produce original works of art for a series of special stamps issued to mark the 250th anniversary of the Royal Academy (RA).
“As a Commonwealth citizen, it was especially important for me to make a visible contribution in a historic public space,” said Mr. Shonibare.
Footballer Walter Tull, who became the first black player to sign for Rangers (just before being killed at the Battle of the Somme), appears on Glasgow’s mailbox in Byres Road. He had played as a striker with Spurs and Northampton Town.
He was featured in a series of stamps issued in 2018 to mark the centenary of the end of World War I and was also the first Black Army officer to command troops in a regular unit.
Mary Seacole, a Jamaican-born nurse who treated wounded British soldiers during the Crimean War, is pictured in Cardiff’s letterbox on King Edward VII Avenue.
And Sir Lenny Henry, comedian, actor, singer, writer and TV presenter and co-founder of Comic Relief, is honored by the Bedford Street Mailbox in Belfast.
Peter De Norville, Head of Diversity and Inclusion at Royal Mail, said: “Black History Month is a great opportunity to celebrate the contributions black people have made to this country for many generations.
“We also use it as an occasion to celebrate the vital work our Black employees do across the country, from the mail bag to the boardroom. “