Under Title 18 USC sec. 2261A, stalking via the U.S. Mail is punishable by imprisonment of more than one year, depending upon the seriousness of the stalker's conduct, which makes the crime a felony.

However, whether the crime is punishable as a felony or misdemeanor is heavily dependent upon exactly what the letter says, and whether the alleged stalker actually engages in a "course of conduct that causes substantial emotional distress to that person or places that person in reasonable fear of the death of, or serious bodily injury..."

Hope this helps.

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