According to Uwe Boll in several interviews and the DVD's audio commentary, no big agencies wanted their stars in the movie. Verne Troyer, Dave Foley, Larry Thomas and J.K. Simmons came to the casting against their agents' wishes because they wanted to be part of the movie.
In early 2007 the New York Post showed a 7 second clip, the infamous window-washer scene, to some of the families of the 9/11-victims, telling them "this is the joke in the new movie Postal by Uwe Boll". Of course they found it tasteless to make fun of 9/11 and its victims in such a fashion. But the scene was the punchline, not the entire joke. The real joke was made on the Taliban 3 minutes before that scene. According to Uwe Boll The NY Post's actions were "more tasteless than any of my movies could ever be," and he considered it another personal attack.
The US release was originally scheduled for Spring 2007, then moved to June 2007, then September 2007. It was finally released May 23, 2008, the day after Indiana Jones and the Kingdom of the Crystal Skull (2008), claiming that Postal will "destroy Indiana Jones at the box office".
In June of 2006, Uwe Boll publicly announced a challenge to his numerous critics to "put up or shut up." Based on certain criteria, Boll would select 5 of his harshest critics to fight in a series of multi-round boxing matches, to be held in Vancouver, British Columbia and broadcast over the Internet. He planned to use footage from these fights in this movie, but that didn't fit the plot, so the idea was dropped. It's claimed that they might be part of the DVD when it's released.
The scene with Osama bin Laden trying to get change back from the payphone was improvised. Larry Thomas came up with the idea when he saw the payphone, and told Uwe Boll, who loved it. In the original script, Osama called George W. Bush with his cellphone.
As stated in the audio commentary on the German DVD, the movie was intended to be more satirical and ridiculous, like "Blues Brothers meets Borat." Executive Producers Steve Wik and Vince Desiderio, didn't like Uwe Boll's approach, so he rewrote it with Bryan C. Knight.
The Seminar Scene with Michael Robinson is stated to be completely improvised with 3 or 4 alternate speeches. Each of them are stated to go on for about 10 minutes and will probably be released on the Director's Cut DVD.
Lindsay Hollister was intended to play "Bitch", the Postal Dude's obese wife. When producers found out Good Luck Chuck (2007) was being filmed in Vancouver at the time, they visited the set for a day. Jodie Stewart fit the role much better because of her weight, so she was approached for the role.