Several of the cast and crew made their first contributions to the series in "Dead Letters", with Wright, Morgan, Wong and Ellis all returning for future episodes.

Black meets up with the detective, Jim Horn (James Morrison), and sees that he is a competent and experienced investigator, although his recent marital separation has left him distracted and on edge.

Surveillance footage of the service yields two leads—a local optician recognizes the suspect as a customer having a glasses lens replaced, and the killer's vehicle is identified.

[8] Lisa Vultaggio, who played the optician used to bait the killer, had previously worked with Morgan and Wong in The X-Files, appearing in the first season episode "Beyond the Sea".

[9] Producer and writer Chip Johannessen felt that the scene in this episode in which a human hair is discovered with a message inscribed upon it was a "perfect" moment, in that it "told you everything about this guy [the killer] ... but you had no idea what he was or what he was going to do next ... you know what kind of crazy motherfucker would do that, but where he is or what he's going to do next, who knows".

[11] Producer John Peter Kousakis recalls having visited the episode's set late during production, having felt that make-up effects supervisor Toby Lindala had been doing "fabulous" work on the series' prosthetic body parts.

[10] "Dead Letters" was first broadcast on the Fox Network on November 8, 1996;[12] and earned a Nielsen rating of 8, meaning that roughly 8 percent of all television-equipped households were tuned in to the episode.

Handlen felt that the episode is "not art, not yet, but it is deeply personal", and praised the opening dream sequence, describing it as "flat-out Lynchian nightmare territory".

However, he noted that the episode's dialogue felt too "flat" and "expository", adding that it serves to draw "attention to themes that were already plastered across the screen in blinding red and black".

[15] Robert Shearman and Lars Pearson, in their book Wanting to Believe: A Critical Guide to The X-Files, Millennium & The Lone Gunmen, rated the episode four stars out of five, describing it as a "gripping and sincere portrait of human ugliness at its most banal".