United States Postal Service
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United States Postal Service
III. Illegal Postal Matter

According to current regulations, liquor, poisons, medicines under certain restrictions, explosives, all articles likely to cause injury or damage, and seditious, obscene, defamatory, or threatening matter are excluded from the mails. Postal regulations restrict unsolicited advertisements that are of a sexually explicit nature. The postmaster general is authorized to prevent mail delivery to persons conducting a fraudulent business.