It is set in a post-apocalyptic and neo-Western version of the United States in the then near-future of the year 2013, fifteen years after an unspecified apocalyptic event that left a huge impact on human civilization and erased most technology. Like the book, the film follows the story of a nomadic drifter (Costner) who stumbles across the uniform of an old United States Postal Service mail carrier, and unwittingly inspires hope through an empty promise of a "Restored United States of America".
In 2013, an unnamed nomad enters the Oregon flatlands, trading Shakespearean performances for food and water. In one of the towns, the nomad is forced into the ranks of the predominant militia, known as the Holnists and run by General Bethlehem. When he escapes, the nomad takes refuge in a dead postman's mail vehicle.
Wearing the postman's uniform and carrying the mail bag, he arrives in Pineview claiming to be a postman from the newly restored US government. The Postman inspires a teenager named Ford Lincoln Mercury and swears him into the postal service. The Postman also meets Abby. When the Postman leaves for the town of Benning, he carries a pile of mail left at the post office door by the townspeople.
During a raid of Pineview, General Bethlehem learns of the Postman’s tales of a restored government and becomes afraid of losing power if word spreads. He burns the American flag and post office, kills Abby’s husband, kidnaps Abby, and attacks the town of Benning. The Postman surrenders, but Abby saves him from execution, and the two escape into the surrounding mountains. A pregnant Abby and an injured Postman ride out the winter in an abandoned cabin.
When spring arrives, they cross the range and run into a girl, who claims to be a postal carrier. She reveals that Ford Lincoln Mercury organized a postal service based on the Postman's story. They have established communications with other settlements, creating a quasi-society and inadvertently spreading hope.
Bethlehem is still fighting to suppress the postal carriers, who are mostly teenagers pitted against a better-equipped enemy. In the face of mounting casualties, the Postman orders everyone to disband and writes a surrender letter to Bethlehem. However, Bethlehem learns to his dismay that the Postman's example has spread farther than he could have anticipated when his men capture a carrier from California, and redoubles his efforts to find the Postman. The Postman, Abby, and a small group of postal carriers travel to Bridge City. When Bethlehem's scouts catch up, the enclave leader, Tom Petty, helps the Postman to escape on a cable car to find volunteers for another army.
In a recitation of King Henry V's speech prior to the Siege of Harfleur, the Postman rallies himself and his troops to war. Bethlehem and his army meet the Postman's army across a field. Knowing the casualties will be great if the armies meet in battle, the Postman instead challenges Bethlehem for leadership, with their troops as witnesses. The Postman wins the fight with inspiration from the "Neither snow nor rain" inscription, and offers Bethlehem a chance to build a new, peaceful world. Bethlehem lunges to shoot the Postman but is shot by his former first officer. The officer surrenders, and the rest of the militia follows.
Thirty years later, in 2043, the Postman's grown daughter speaks at a ceremony unveiling a statue in tribute to her late father. The modern clothing and technology show that the Postman's actions have rebuilt the United States and possibly the other nations of the world.
On his personal website, author David Brin reveals that while studios were bidding for The Postman, his wife decided during a screening of Field of Dreams that Kevin Costner should portray The Postman. Brin agreed that the emotions evoked by Field of Dreams matched the message he intended to deliver with his novel. A decade later, after learning Costner would be cast as the lead, Brin said he was "thrilled". Costner discarded the old screenplay (in which the moral message of the novel had been reversed) and hired screenwriter Brian Helgeland; Brin says the two of them "rescued the 'soul' of the central character" and reverted the story's message back to one of hope.
In an interview with Metro before filming began, Brin expressed his hope that The Postman would have the "pro-community feel" of Field of Dreams instead of the Mad Max feel of Costner's other post-apocalyptic film Waterworld. Brin said that, unlike typical post-apocalyptic movies that satisfy "little-boy wish fantasies about running amok in a world without rules", the intended moral of The Postman is that "if we lost our civilization, we'd all come to realize how much we missed it, and would realize what a miracle it is simply to get your mail every day."
The Postman was filmed in Metaline Falls and Fidalgo Island, Washington; central Oregon; and southern Arizona around Tucson and Nogales.
The Postman received overwhelmingly negative reviews from critics.
Stephan Holden of The New York Times criticized the movie for its "bogus sentimentality" and "mawkish jingoism". Roger Ebert described The Postman as "good-hearted" yet "goofy... and pretentious". However, Ebert recognized the movie as a failed parable, for which he said the viewers "shouldn't blame them for trying". On Siskel & Ebert, Ebert and Gene Siskel gave the film "two thumbs down", with Siskel calling it "Dances with Myself" (in reference to Costner's Oscar-winning film Dances with Wolves) while referring to the bronze statue scene.
According to review aggregator Rotten Tomatoes, 3 out of 32 film critics gave the film a positive review, with a "Rotten" score of 9% and an average rating of 3.8/10. Metacritic gives the film a metascore of 29 out of 100 based on 14 reviews.
The film was a notable failure at the box office. The first four days after opening brought in only $5.3 million on 2,207 screens. Produced on an estimated $80 million budget, it returned less than $18 million.
The film was subsequently released on VHS and DVD on June 9, 1998, and on Blu-ray Disc on September 8, 2009.