Residents living in border areas have been left asking if they are receiving a first class service after it emerged that letters sent to destinations just yards away are travelling hundreds of miles.
Barry McElduff, Sinn Fein MLA for West Tyrone, said he cannot understand why letters and parcels must go on such long journeys, even though "you could throw a paper aeroplane" between some of the border towns involved.
Letters between places such as Lifford in Co Donegal and Strabane in Co Tyrone - just hundreds of metres apart - travel to Athlone, Dublin and then Belfast before arriving at their intended destination, postal chiefs have confirmed.
"So much for the carbon footprint and so much for efficiency in employing resources," Mr McElduff said.
"I have dealt with many people who have moved just inside the border with either Co Tyrone or Co Donegal who are mystified about the journey a letter has to take.
"I spoke to one young woman whose family had just moved into Donegal just a mile from their old home and her exam results arrived days after all her friends had got theirs.
"You could practically throw a paper aeroplane between Strabane and Lifford, such is the distance between them.
"It is a major issue for a lot of people and is something the Government will have to look at."
Mr McElduff has in the past helped organise a number of cross-border initiatives, including the setting up of an out-of-hours GP service.
A spokeswoman for An Post in the Republic said that mail posted in Lifford and meant for Strabane travels from Lifford to Athlone Mail Centre, from there to Dublin Mail Centre, then to Belfast and then on to Strabane ? for two-day delivery.
Mail from Strabane to Lifford makes the same journey in reverse.
"An Post sorts mail at its automated hubs for onward despatch to all national and international destinations," the spokeswoman explained.
"The main hubs are located in Athlone, Portlaoise, Dublin and Cork.
"There is a next day delivery between Dublin and Belfast."
Royal Mail defended their arrangements too.
"All mail posted in Strabane, including cross-border post, goes to the Northern Ireland Mail Centre in Mallusk on the outskirts of Belfast," said a spokeswoman.
"Mail is then sent by road to An Post's Dublin Mail Centre for onward delivery in Republic of Ireland.
"Royal Mail and An Post have special operational procedures in place to ensure that mail flows as efficiently as possible on a daily basis between Northern Ireland and the Republic.
"Items for either destination are handled separately in the mail centres of both Royal Mail and An Post where sorting machines are capable of processing mail at a rate of 30,000 plus items per hour, which is clearly much quicker than manual sorting.
"Mail is then transported in bulk by road between the two postal authorities for onward delivery.
"This arrangement is the most effective way of ensuring that cross-border mail is handled as efficiently and as effectively as possible.
"Royal Mail carefully monitors performance in this area as with every other aspect of our operations."