Published Thursday, 29 October 2009
In Northern Ireland, the sorting depot at Mallusk will be closed and there will be no deliveries on Saturday.
Royal Mail has condemned the industrial action and is urging the Communication Workers Union to come back to the table.
Their managing director Mark Higson says the central issue remains the CWU's opposition to essential modernisation plans.
He said "We have repeatedly asked for a common sense approach that allows a strike-free Christmas while we talk about the future yet even that seems too much for the CWU to accept."
But Bobby Weatherall from the CWU in Northern Ireland says they are actively seeking a resolution to the dispute.
"Obviously we do not want this to affect the general public and the small businesses. What we are trying to do is to get the proper deal, the proper ground to move forward," he said.