SYDNEY, N.S. -- Gerard Dunn has found an unexpected best friend in his local postman who makes daily house calls -- sometimes with the help of a supervisor -- to deliver an "overwhelming" torrent of fresh cards for him to look through.

His Sydney, N.S., home is packed with containers full of letters, notes, and postcards after a tweet from his daughter Miriam went viral last month asking people to mail him their best wishes for his 92nd birthday on Tuesday -- it being the first birthday in a very long time that he will spend without his beloved wife, Ellen, who died in March.

Since that tweet, Gerard has received thousands of cards from people all over the world, including Europe, Australia, Africa, and the Americas.

"Oh my goodness. It's an experience," he said.

The tweet even elicited a response from Prime Minister Justin Trudeau who sent Gerard a card wishing him a happy birthday.

Other notable cards include one from a woman he saved from drowning as a girl, who felt the need to reach out and thank him decades later.

Another woman sent a card that said "Happy Birthday Dad." Inside, she wrote that she got the card for her own father, but he passed away before she could give it to him. She didn't know what to do with it until she saw the now-famous tweet.

Miriam said she still finds the response hard to believe.

"I think it's impossible for Dad, or I, to really fathom how much impact this has had on so many people around the world," she said.

"And I think it's going to take a little time, and a little distance, to really understand, to see the big picture."

Miriam continues to document the cards that come in on her Twitter account.

When asked what 4,000 cards -- their latest estimate -- looks like, she said: "Like a huge mess in your house."

Some cards contain snippets of the lives of the people who wrote them. Some included photographs, maps, calendars, or even books about the places they're from. A man in Amsterdam sent some chocolates.

But Miriam said the best part is that her plea seems to have re-invigorated the lost art of letter-writing, which has been gradually replaced by emails, text messages, and tweets.

"What's so remarkable is the thought, time and care that people are taking to communicate with Dad," she said.

"Writing genuine letters, filling in the news, and describing their lives, talking about the things they think about, the things they like, and asking questions. And it's so reminiscent of days gone by when people wrote long letters that were kind of a stream of consciousness."

She said that since her tweet went viral, Our Lady of Fatima Catholic school in Chatham, Ontario -- where Gerard's granddaughter teaches --launched a program for its students to write letters to local seniors.

Handling the mountain of mail was becoming a bit of a challenge for Gerard, so he enlisted his family to help sort through it all.

"It still impresses me so much, that the people who sent cards were so happy to do so, and so sincere about it all," he said. "That's got me overwhelmed with joy and thankfulness."

Gerard had always received cards from his wife for the many birthdays, holidays and anniversaries they shared over more than six decades of marriage, retrieving his favourites to adorn his home for each special occasion.

And he believes she would be thrilled to know that his story has touched so many people around the world.

"My wife was a very, very, very special individual, and that's not just husband and wife talk," he said.

"Her greatest gift was that she, no matter who she met or where ... she always made the other party feel more important and happier than they did before. It was something to watch, and I watched for 60 years. I can't get used to it, even now. But she's still watching over us, I know that."

Once the cards stop coming in, the Dunn family will begin the monumental task of answering them. Gerard said he has no plans to throw any away, and is still trying to figure out how best to express his gratitude to everyone.

As for having Miriam send out another tweet on his behalf, he chuckled at that suggestion.

"I'll have to put a rein on her and say: 'no more tweets for many years!' ... Maybe for my 100th," he said.