dead letter office...

from www.wikipedia.com:

"The United States Postal Service started a dead letter office in 1825 to deal with undeliverable mail. Approximately 57 million items end up in this office every year, where enclosed items of value are removed and the correspondence is destroyed. When enclosed items are deemed to be of obviously exceptional value, efforts may be made to return them to the sender. Items of value that cannot be returned are sold at auction. Except for pornography and firearms, everything that can be lost in the mail is included at auction. The auctions also occasionally include items seized by postal inspectors and property being retired from postal service.
These facilities are now known as mail recovery centers (MRC). Other former names include dead letter branch and dead parcel branch. These facilities are not unique to the US Postal Service, and go by different names in other countries. The USPS mail recovery centers are located in Atlanta, Georgia and Saint Paul, Minnesota. Since 2004, the postal auctions have been held only in Atlanta. These auctions include not only material lost in the US but also material from other national postal authorities who consign them to the USPS for auction.
The Canadian equivalent of the dead letter office is located in Mississauga, Ontario."