Tom Jackson picks up postcards at car boot sales and in charity shops - sharing a picture and one line of text with his 40,000 followers on @PastPostcard.
The content ranges from the mundane - "I wish you were here" - to the surprising - "Dear Auntie - you will be surprised to hear I am going to prison tomorrow."
It has proven such a hit that it is now being turned into a book and an exhibition.
So what makes someone else's holiday so fascinating?
Mr Jackson, 53, says most postcards are "actually pretty boring".
But only sharing part of the message leaves the reader with "more questions than answers" he says.
He started the Twitter account last year during a quiet moment at work, and has since shared nearly 4,000 postcards.
"If seeing the whole card was really interesting, everyone would be buying old postcards," he says.
The account took off after the poet Ian McMillan and comedian Danny Baker retweeted his postcards, he said.
"I do it all the time between things. I haven't spent a fortune, you might pay 50p for an old card in a charity shop."
The book, Postcard from the Past, was published on Thursday. Gatwick Airport will next week display a collection of 250 of the postcards.
Most of his collection was posted in the 1960s and 1970s when holidays - and foreign travel - became more affordable.
Research suggests that we are now far less likely to go to the trouble of writing one ourselves.
Just 28% of people in the UK sent a postcard from their last holiday, compared with 70% in 1997, according to a study of 2,000 adults.
However, the survey, carried out for Gatwick Airport, found that people aged 18-35 - the so-called "millennial" generation - bucked the trend.
Some 38% of millennials said they had sent a postcard from their last holiday, compared with 24% of those aged 35 and over.
"The trend has been for postcards going out of fashion, and perhaps the post being less reliable," says Mr Jackson.
"Maybe there's a small blip canning that trend."
He says people are still "intrigued" by old postcards, especially if they are funny or have a resonance with today.
But anyone who wants to read the rest of a postcard message will be disappointed.
"Sometimes people will want to see the whole message - I don't reply, I never talk on the feed," says Tom.
Sending postcards home is no longer the holiday staple it once was, but a Twitter account sharing snippets from other people's trips is proving the appetite for the handwritten updates remains.