Tenna is almost certainly referring to Spamton when he says “the mailman.” The fan discussion and Chapter 3 references point to Spamton as the “mailman” joke, tied to his spam-email theme rather than an actual postal job.

Why that fits

  • Spamton is already strongly associated with spam mail and email imagery, so “mailman” works as a playful in-universe label.
  • Chapter 3 dialogue and discussion around Tenna’s lines are widely interpreted as a direct nod to Spamton.
  • The wording appears to be more metaphorical than literal, matching Deltarune’s habit of character-based wordplay.

Quick scoop

In plain terms: Tenna’s “mailman” is Spamton.