Editing Letter box (section)

===United States===
Numerous designs of mailboxes with improved construction and security have been [[patent]]ed in recent years, particularly in the United States.<ref>Frameless mail slot - Patent D480200; Airtight mail slot - Patent 2437319; Mail slot immobilizer - Patent D443125; Mail slot pouch assembly - Patent 4069965; Mail slot alarm - Patent 5382945; etc.{{Verify source|date=February 2012}}</ref> In 2001, the [[USPS]] first approved designs for locking curbside mailboxes to stem a rise in identity and mail theft.<ref name="Reference7A"/> With these secure designs, the incoming mail is placed into a slot or hopper by the mail carrier, where it drops into a secure locked compartment for retrieval by only the homeowner (who retains a key or combination to the lock). Locking mailboxes are generally constructed of heavy-gauge steel or aluminum plate, though some models are made of [[Rotational molding|roto-moulded]] polymer plastic.<ref name="BERN"/>

Because of the increased risk of vandalism to curbside mailboxes, numerous vandal-resistant boxes made of composite plastic or heavy-gauge steel or aluminum plate have also entered the market. Some composite mailboxes made of resilient polymer plastics and mounted on ground spikes can resist severe impacts from baseball bats or even being run over by a vehicle.<ref name="BERN"/>

In 1978, steady increases in postal service costs caused the USPS to insist on either curbside or [[centralized mail delivery]] for new suburban neighborhoods and developments.<ref>Judis, John B., ''Mission Impossible'', ''[[New York Times]]'', September 25, 1988{{Verify source|date=February 2012}}</ref><ref>[https://www.washingtonpost.com/wp-dyn/content/article/2007/06/16/AR2007061601213.html You've Got Mail... a Block Away], Philip Rucker, ''[[Washington Post]]'', 17 June 2007</ref> A 1995 cost delivery study published in a USPS Operations handbook listed per-address annual delivery costs as: Door-to-door, $243; Curbside, $154; Cluster/flock Box (centralized mail delivery), $106.<ref>{{cite news|last=Pappas |first=Max |title=Cluster Boxes, Not Door-to-Door Delivery |publisher=Providence, Rhode Island Journal |url=http://lexingtoninstitute.org/166.shtml |url-status=dead |archive-url=https://web.archive.org/web/20081022232958/http://lexingtoninstitute.org/166.shtml |archive-date=October 22, 2008 }}</ref><ref>USPS Handbook PO-630, ''Post Offices Serving DOD Installations'', p.47</ref>

Large apartment buildings usually have a cluster/flock of mailboxes for all units, located in the entry lobby or in a nearby dedicated mailroom. There often is a special lock box (also called a "key keeper" or "Knox box") located at the outside entrance, which either gives access to a front door key or directly activates the front door [[electric strike]], to allow the mail delivery person to enter the building. A similar "Arrow lock" is usually located on the centralized mailbox, to allow the entire unit to be opened for efficient filling of individual mailboxes.<ref name="USPS-wall">{{cite web|title=U.S. Postal Service Standard Wall-mounted Centralized Mail Receptacles|url=http://about.usps.com/publications/engineering-standards-specifications/spusps-std-4c001/welcome.html#figure13|website=about.usps.com|publisher=USPS|access-date=2017-03-31|language=en|quote=SPUSPS-STD-4C001}}</ref>

[[File:FEMA - 20767 - Photograph by Robert Kaufmann taken on 12-21-2005 in Louisiana.jpg|thumb|left|A USPS CBU Mail Station]]

In the US, a property with a single mailing address but with multiple mail recipients may utilize a community mail station designated '''CBU''', or '''Cluster Box Unit'''. CBUs are typically stand-alone units that have locked individual compartments for each tenant in an apartment building, a trailer or mobile home park, or an office center.

By policy, the USPS is reluctant to establish direct to door delivery to new addresses, and now requires special approvals to initiate this service (Postal Operations Manual, Section 631.2) Instead, the USPS has insisted upon centralized mail delivery in virtually all newly constructed residential housing developments, condominiums, and gated communities by requiring or incentivizing the builder or developer to install larger '''NDCBU''' ('''Neighborhood Delivery Collection Box Unit''') stations. CBUs and NDCBUs are both commonly known as ''cluster mailboxes''. The NDCBU is a centralized community mail station with compartments for the centralized delivery of mail to multiple recipients at multiple addresses within a single neighborhood development or community.<ref name="WIL">Williamson, Sarah L., ''[https://archive.today/20110912055809/http://www2.hickoryrecord.com/news/2011/aug/22/police-name-suspect-mailbox-break-ins-thefts-ar-1322546/ Police name suspect in mailbox break-ins, thefts]'', Hickory Daily Record, retrieved 23 January 2012</ref>

In new housing developments, the NDCBU location is fixed by the developer, not the USPS, and may be located hundreds of yards away from the addressee's actual residence.<ref name="RUC">Rucker, Philip, ''[https://www.washingtonpost.com/wp-dyn/content/article/2007/06/16/AR2007061601213.html You've Got Mail, A Block Away]'', 17 June 2007, retrieved 23 January 2012</ref><ref name="ENT">[http://health.ktnv.com/story/10359672/entire-mailbox-cluster-stolen?clienttype=printable "Entire Mailbox Cluster Stolen"], Channel 13 Action News, Las Vegas, 13 May 2009, retrieved 23 January 2012 {{webarchive |url=https://web.archive.org/web/20131015084640/http://health.ktnv.com/story/10359672/entire-mailbox-cluster-stolen?clienttype=printable |date=October 15, 2013 }}</ref> A parcel locker for receipt of packages and a separate compartment for outgoing mail are usually built into the station.<ref>{{cite news|publisher=Nations Building News |title=Costly Mailbox Rules Take Effect in September |url=http://www.nbnnews.com/NBN/issues/2006-07-24/Multifamily/index.html |url-status=dead |archive-url=https://web.archive.org/web/20080705182634/http://www.nbnnews.com/NBN/issues/2006-07-24/Multifamily/index.html |archive-date=2008-07-05 }}</ref> The mail carrier will have a key to a large door on one side that reaches all the compartments, and the residents or tenants will each have a key to the door into their individual compartment on the other side.

The location of the NDCBU in a community or business center is extremely important, since neighborhood cluster box installations located in remote or poorly lighted areas invite large-scale mail theft or vandalism.<ref name="ENT"/><ref name="LIS">Lisaius, Som, ''[http://www.kold.com/story/16439200/mail-thieves-hit-sierra-vista-mobile-home-park Mail thieves hit Sierra Vista mobile home park]'', KOLD News, 10 January 2012, retrieved 23 January 2012</ref><ref name="ROS">Roseville Patch Staff, ''[http://roseville-ca.patch.com/articles/crime-watch-gas-siphoning-vandalized-cars-mailboxes Crime Watch: Gas Siphoning, Vandalized Cars, Mailboxes]'', The Roseville Patch, retrieved 23 January 2012</ref><ref name="CITY">''[http://www.cityofvancouver.us/nhoodtools.asp?tool=4&itemID=29219 Mailbox Break-in and Theft of Mail]'', City of Vancouver, Washington, retrieved 23 January 2012 {{webarchive |url=https://web.archive.org/web/20110131142544/http://www.cityofvancouver.us/nhoodtools.asp?tool=4&itemID=29219 |date=January 31, 2011 }}</ref><ref>Auslander, Jason, ''Police Charge Man in String of Mailbox Break-ins'', The Santa Fe New Mexican, 30 July 2009</ref><ref name="HAM">Hamer, Roger, and Smollen, Gary, ''[http://www.wowt.com/home/headlines/Cluster_Crime_in_Council_Bluffs_131288189.html Cluster Crime In Council Bluffs]'', Channel 6 News, 6 October 2011, retrieved 23 January 2012</ref><ref name="ROSE">Rosenberg, Katherine, ''Thieves steal mail from 130 Phelan households and 18 cluster mailboxes'', Victorville Daily Press, 4 January 2006</ref><ref>Postal Employee Network, ''[http://www.postalemployeenetwork.com/images/ndcbu-damaged.jpg CBU Theft Photo, Phelan, CA]'', 4 January 2006, retrieved 23 January 2012</ref><ref>''Cluster Mailbox Burglary Prompts Investigation'', The Orlando Sentinel, 29 May 2004</ref> Even when located in a high-traffic location or inside a gated community, the NDCBU is a tempting target for thieves attracted by the possibility of recovering checks, cash, identifying information, or other valuables from multiple victims.<ref name="WIL"/><ref name="ENT"/><ref name="LIS"/><ref name="CITY"/><ref name="HAM"/><ref name="ROSE"/><ref>City of Ventura, California, ''[http://www.cityofventura.net/pd/crime/prevention/burglary Home & Neighborhood Safety: Cluster Mailboxes] {{webarchive|url=https://web.archive.org/web/20120202214252/http://www.cityofventura.net/pd/crime/prevention/burglary |date=2012-02-02 }}'', retrieved 23 January 2012: "Cluster mailboxes are those that house mail receptacles for several residences...They make particularly attractive targets for thieves, as once the back of the box is breached, all of the individual sections become accessible and mail from many households can be taken in a very short period of time."</ref><ref>Arata Jr., Michael J., ''Identity Theft For Dummies'', Hoboken, NJ: Wiley Publishing Inc., {{ISBN|978-0-470-56521-6}} (2010), pp. 10-11</ref> A 2008 [[RAND Corporation]] study, citing USPS statistics collected between 2004 and 2007, found that NDCBU thefts constituted 52.7% of all urban neighborhood mail thefts and 76.6% of all rural neighborhood mail thefts from locations with more than one mailbox, with higher-income ZIP code zones having a substantially higher number of thefts than low-income ZIP code zones.<ref>Davis, Lois M., et al., ''The Role of the United States Postal Service in Public Safety and Security: Implications of Proposed Relaxation of the Mailbox Monopoly'', Washington, D.C.: United States Postal Service/[[RAND Corporation]], {{ISBN|978-0-8330-4615-4}} (2008)</ref>