Walter Reed Army Medical Center officials want to remind those individuals who want to show their appreciation through mail to include packages and letters, addressed to "Any Wounded Soldier" that Walter Reed will not be accepting these packages in support of the decision by then Deputy Undersecretary of Defense for Transportation Policy in 2001. This decision was made to ensure the safety and well being of patients and staff at medical centers throughout the Department of Defense. In addition, the U.S. Postal Service is no longer accepting "Any Service Member" or "Any Wounded Service Member" letters or packages. Mail to "Any Service Member" that is deposited into a collection box will not be delivered.
The entire statement can be read here