FYI:
http://usgovinfo.about.com/library/weekly/aatroopmail.htm
EXCERPT:
The US Postal Service has announced that APO ZIP codes for US military units in Kuwait and countries near the Iraq war zone will be made available only to family members and close friends of deployed soldiers. Postal officials stated that the limitation had been imposed due to anthrax and other terrorist threats.
Programs that allowed the general public to send mail addressed to "Any Service Member" were cancelled more than a year ago. While these programs were popular with the public during Desert Storm and other operations, officials said security concerns and transportation constraints with military mail led to their cancellation. Web sites such as http://anyservicemember.navy.mil, and Army Knowledge Online email have been suggested as alternate means to contact soldiers.