page_title: Dead letter mail
section_title: Dead letter office
hierarchical_section_title: Dead letter mail / Dead letter office
caption_attribution_description: English: Dead letter office, September 22, 1922. Probably Washington, D.C.
context_page_description: Dead letter mail or undeliverable mail is mail that cannot be delivered to the addressee or returned to the sender. This is usually due to lack of compliance with postal regulations, an incomplete address and return address, or the inability to forward the mail when both correspondents move before the letter can be delivered. Largely based on the British model that emerged in the late eighteenth century, many countries developed similar systems for processing undeliverable mail.
  The term 'dead mail' is perhaps a misnomer, and several jurisdictions have opted for the use of the term 'undeliverable mail' as more clearly representing the status of the item whose transmission has been impeded. As it is performed by internal departments within postal administrations, little information about the dead letter office function has ever been made public. A few journal articles and at least one recently published book dealing with this topic have appeared.
  Classification as a dead letter is one of the few instances where postal personnel are allowed to violate secrecy of correspondence, ostensibly to search for clues as to the letter's origin or destination.
context_section_description: A dead letter office (DLO) is a facility within a postal system where undeliverable mail is processed. Mail is considered to be undeliverable when the address is invalid so it cannot be delivered to the addressee, and there is no return address so it cannot be returned to the sender.
  At a DLO, mail is usually opened to try to find an address to forward to. If an address is found, the envelope is usually sealed using tape or postal seals, or enclosed in plastic bags and delivered. If the letter or parcel is still undeliverable, valuable items are then auctioned off while the correspondence is usually destroyed. Despite this practice, in the past some undeliverable envelopes were acquired by philatelists.
  Dead letter offices go by different names in different countries. Other names include returned letter office or undeliverable mail office.
caption: Dead letter office, probably in Washington, D.C.; September 1922
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