The Miracle of the Cards (2001)

"The Miracle of the Cards" is based on the true story of Marion Shergold and her son, Craig, an eight-year-old English boy who had a brain tumor. Several events convinced Marion that God was leading her to a cure for Craig and that the get-well cards he was receiving had the power to keep him alive, so she launched a worldwide campaign to break the Guinness record for receiving the most get-well cards. At the time, the world record seemed an impossible 1,000,265, but Craig received over 350 million cards from all over the world. Against the advice of her doctors, Marion followed one of those cards to America for Craig's miraculous cure.

Unfortunately the movie The Miracle of the Cards is not yet available on HBO Max.