The Danish postal service will deliver its last letter on 30 December, ending a more than 400-year-old tradition.

Announcing the decision earlier this year to stop delivering letters, PostNord, formed in 2009 in a merger of the Swedish and Danish postal services, said it would cut 1,500 jobs in Denmark and remove 1,500 red postboxes amid the “increasing digitalisation” of Danish society.

Describing Denmark as “one of the most digitalised countries in the world”, the company said the demand for letters had “fallen drastically” while online shopping continued to increase, prompting the decision to instead focus on parcels.

It took only three hours for 1,000 of the distinctive postboxes, which have already been dismantled, to be bought up when they went on sale earlier this month with a price tag of 2,000 DKK (£235) each for those in good condition and 1,500 DKK (£176) for those a little more well-worn. A further 200 will be auctioned in January. PostNord, which will continue to deliver letters in Sweden, has said it will refund unused Danish stamps for a limited time.

Danes will still be able to send letters, using the delivery company Dao, which already delivers letters in Denmark but will expand its services from 1 January from about 30m letters in 2025 to 80m next year. But customers will instead have to go to a Dao shop to post their letters – or pay extra to have it collected from home – and pay for postage either online or via an app.

The Danish postal service has been responsible for delivering letters in the country since 1624. In the last 25 years, letter-sending has been in sharp decline in Denmark, with a fall of more than 90%.

But evidence suggests a resurgence in letter-writing among younger people could be under way.

Dao said its research had found 18- to 34-year-olds send two to three times as many letters as other age groups, citing the trend researcher Mads Arlien-Søborg, who puts the rise down to young people “looking for a counterbalance to digital oversaturation”. Letter-writing, he said, had become a “conscious choice”.

According to Danish law, the option to send a letter must exist. This means that if Dao were to stop delivering letters, the government would be obliged to appoint somebody else to do it.

A source close to the transport ministry insisted there would not be any “practical difference” in the new year – because people would still be able to send and receive letters, they would simply do so through a different company. Any significance around the change, they said, was purely “sentimental”.

But others have said there is an irreversible finality to it. Magnus Restofte, the director of the Enigma postal, the telecommunications and communications museum in Copenhagen, said in the event that it were no longer possible to use digital communications “It’s actually quite difficult to turn back [to physical post]. We can’t go back to what it was. Also, take into consideration we are one of the most digitalised countries in the world.”

Under the MitID scheme – Denmark’s national digital ID system, used for everything from online banking to signing documents electronically and booking a doctor’s appointment – all official communications from authorities are automatically sent via “digital post” rather than by mail.

While there is the option to opt out and instead receive physical mail, few do. Today, 97% of the Danish population aged 15 and over is enrolled in MitID and only 5% of Danes have opted out of digital post.

The Danish public, said Restofte, had been “quite pragmatic” about the change to postal services because very few people received physical letters in their postboxes any more. Some younger people have never sent a physical letter.

But the scarcity of physical letters has increased their value. “The funny thing is that actually receiving a physical letter, the value of that is extremely high,” said Restofte. “People know if you write a physical letter and write by hand you have spent time and also spent money.”

Announcing their decision earlier this year, Kim Pedersen, the deputy chief executive of PostNord Denmark, said: “We have been the Danish postal service for 400 years, and therefore it is a difficult decision to tie the knot on that part of our history. The Danes have become more and more digital and this means there are very few letters left today, and the decline continues so significantly that the letter market is no longer profitable.”