United States Postal Service The United States Postal Service said cards and packages need to be mailed no later than these dates for an expected delivery by Dec. 25: Dec. 15: USPS Retail Ground Service, Hawaii to mainland Priority Mail and Hawaii to mainland First-Class Mail Dec. 18: First-Class Mail (including greeting cards), First-Class packages (up to 15.99 ounces) and Alaska to mainland First-Class Mail Dec. 19: Priority Mail, Alaska to mainland Priority Mail Dec. 19: Alaska to mainland Priority Mail Dec. 21: Alaska to mainland Priority Mail Express and Hawaii to mainland Priority Mail Express Dec. 23: Priority Mail Express The Postal Service recommends the following mailing and shipping deadlines for expected delivery by Dec. 25 to Air/Army Post Office/Fleet Post Office/Diplomatic Post Office: