Pete Nowacki with USPS says it is always recommended that you get those holiday cards, letters and gifts sent as early as possible.
Deadlines for Parcel Post: December 15th, Letters and Cards December 20th, Priority Mail: December 21st and Express Mail: December 22nd.
Some letters and parcels sent shortly after these holiday shipping cut-off dates still might arrive before Christmas, if normal holiday conditions prevail. Even so, do yourself a favor and get your holiday mailing done early this year.The USPS places all Air/Army Post Office and Fleet Post Office zip-coded mail on special charter flights, commercial airlines, and military aircraft to reach armed service personnel as quickly as possible.
All military mail, regardless of destination, is sent by domestic mail rate. International rates do not apply to military mail delivery.