Here are the official mailing dates:
The Naval Supply Systems Command's (NAVSUP) Postal Policy Division, in cooperation with the U.S. Postal Service and military postal officials from all of the services, notes it is not too early to mail your 2004 Christmas cards, letters and packages to and from military addresses overseas. In fact, everyone is encouraged to beat the last minute rush and bring holiday mail and packages to the nearest U.S. Post Office, Army/Air Force Post Office (APO), or Navy/Marine Corps Fleet Post Office (FPO) by the recommended dates listed below. For military mail addressed to APO and FPO addresses, the mailing dates are:
Parcel Post - November 13
Space Available - November 27
Parcel Airlift - December 4
Priority Mail, First Class cards and letters - Mailing date is December 11, to all locations, except for locations starting with ZIP 093. For all locations starting with ZIP 093 the mailing date is December 6.
Express Mail - December 20 to locations where Express Mail service is available. Check with your local post office to determine which APO/FPO addresses can receive Express Mail. Note: This service is not available to ships.
For military mail from APO and FPO addresses, the mailing dates are:
Space Available - November 20
Parcel Airlift - December 4
Priority Mail, First Class cards and letters - December 11
Express Mail - December 18 from APO/FPO addresses where Express Mail can be accepted. Check with your local military post office to determine if they can accept Express Mail. Note: This service is not available from ships.