What is the definition of Mailed Fear?

"Mailed fear" is a term that humorously describes the act of sending something that evokes dread or anxiety via mail, like an unsolicited horoscope or a cryptic message from the universe that says, "You'll never be happy again."

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Here's an unsettling example sentence: "The post office delivered mailed fear in the form of a vintage horror novel titled 'The Haunting of Hill House: A Guide for Scared People.'"