Search Now, Inspect for Fentanyl Act of 2018 or the SNIFF Act This bill requires a U.S. Postal Service employee at an international service center who has been properly trained to inspect the contents of a package that originated outside the United States and is addressed to a U.S. location to inspect the contents of such package, without obtaining a search warrant, if there is probable cause to believe that such package contains illicit materials, including matter that is nonmailable. Such requirement shall not apply if the employee believes that inspecting the contents of such a package would pose a risk of personal injury to the employee or other individuals.