Dangers of the Mail faced criticism and objections at the time of its creation for lewdness and in the 21st century for stereotypical portrayals of Native Americans and depictions of sexualized violence causing a hostile workplace environment.

[1] Researcher Jessy Ohl describes the central painting as showing three "naked white women (being) scalped in a sexually explicit manner" in the bottom right hand of the artwork, where they are shown kneeling and bent awkwardly toward the sky and ground by three Native Americans.

[1] Rowan instructed Mechau to finish the work and get it installed as quickly as possible on the expectation that once the mural was in effect a fait accompli, the objections would eventually blow over.

This time, several EPA employees argued that the mural, along with five others in the building, conveyed stereotypical portrayals of women and Native Americans and contributed to a hostile work environment.

[9] In 2007, the General Services Administration, which is responsible for the management of federal buildings in the United States, agreed to install a movable screen in front of Dangers of the Mail and to "incorporate revised interpretative materials to address the history of the art and the controversy associated with the mural".

A "comprehensive interpretive program" was developed for all 22 murals in the building, including Mechau's Dangers of the Mail and Pony Express, Lockwood's Opening of the Southwest and Consolidation of the West, William C. Palmer's Covered Wagon Attacked by Indians, and Karl R. Free's French Huguenots in Florida, which were the ones named in the filing.

[10] Ohl, in 2019, wrote, "Far from reflecting an impartial or even faintly recorded 'History of the Post', Dangers of the Mail instead condenses titillating imagery of Western expansion epitomized in early American literature, film, television, and theatrical performance.