Are there laws against sending harassing letters via the us mail?

Yes, there are laws against sending harassing letters via the U.S. mail. Under 18 U.S.C. § 876, it is a federal offense to send threatening communications through the mail, which includes harassing letters. Additionally, state laws may also apply, which can impose further penalties for harassment or stalking through written communication. Victims can report such offenses to law enforcement for investigation and potential legal action.