David Mundell MP, told ITV Border about the post office:
A plaque has been unveiled at Sanquhar post office, recognising it as the world's oldest working post office.
What's thought to be the world's oldest working post office is celebrating its 300th birthday. Sanquhar Post Office dates back to 1712 and is older than rivals in Sweden and Chile, according to local historians.
The site started out as a staging post for runners moving mail on foot and horseback.
David Mundell MP will present a plaque to the subpostmistress during a ceremony.
The world's oldest post office in Sanquhar in south west Scotland is celebrating its 300th anniversary this year.
Members of the local heritage society are campaigning for national recognition to be given to the building.