Monday is the busiest mailing day of the year for the United States Postal Service. Pella Postmaster Danielle Lloyd says that first class mail needs to be in the system by Friday, priority mail by Saturday, and priority mail express by Monday the 23rd. Lloyd adds that new rules this year prohibit the mailing of lithium batteries or perfume. She says batteries are ok if they are inside a device, otherwise they will be not permitted to be shipped.