postalref

DSF2

DSF2 is a USPS address product that tells whether a ZIP + 4 coded address is a known address record in the USPS delivery file. It also gives an address's attributes, such as vacant, residential, business or seasonal. DSF2 processing is one approved way to put mail in walk sequence without a simplified address.

Updated October 31, 202633 sources

What it is

DSF2 is an Address Management Service that checks mailing address accuracy, identifies address types and gives walk sequence statistics. Its database holds every deliverable mailing address in the United States. It is an upgrade to an earlier service called the Delivery Sequence File.

USPS licenses DSF2 to businesses that provide, or plan to provide, address verification and list processing services. The annual license fee is $230,800.00. A licensee may use DSF2 only on address lists, for address hygiene, attribute assignment and sequencing before mailing.

DSF2 does not say who owns, occupies or lives at an address, or confirm that anyone resides there. Correcting the problems it finds can reduce undeliverable-as-addressed pieces.

The base DSF2 tables are about 500 MB and take extensive programming to connect to ZIP + 4 matching software. Sixteen more hash tables return the address attributes. A licensee also needs the eLOT and Delivery Statistics products. USPS sends DSF2 updates monthly through Electronic Product Fulfillment. The two most recent releases are available to download.

How it works

The input to DSF2 is a 9-digit ZIP + 4 code and a parsed address. DSF2 only identifies known address records, so it cannot assign a ZIP + 4 code or answer for an address without one.

A licensee runs each customer list through these steps.

  1. Run the list through CASS Certified software for a 9-digit ZIP Code and a parsed address.
  2. Query the DSF2 tables, which answer each address with a return code.
  3. For each negative answer from the A hash table, query the False Positive table.
  4. Probe every address attribute table for each record.
  5. For walk sequence, get each address's walk sequence number from eLOT.
  6. Return the processed list to the customer within seven business days.
  7. Give the customer the Delivery Sequence Invoice Documentation report for walk-sequence discounts.

Return codes

Each address DSF2 checks gets a one-letter return code, or a blank. Delivery Point Validation, a related USPS product, makes the same check on a ZIP + 4 coded address, and the codes cover both.

CodeMeaning
YConfirmed for the primary number and any secondary number.
DConfirmed for the primary number only, with the secondary information missing.
SConfirmed for the primary number only, with a secondary number present but invalid, or a trailing letter dropped to match.
NThe primary number failed to confirm.
blankThe address was not presented to DPV/DSF2.

An enhanced set of return codes adds R: the address is confirmed, but it is on a phantom route and USPS does not deliver to it.

Licensees also give customers the standard footnotes, codes such as AA, input address matched to the ZIP + 4 file.

Address attributes

DSF2 derives each address's attributes from separate tables. A licensee must probe every attribute table for every record, whether or not the customer asked for the attributes.

AttributeWhat it marks
BusinessA business address.
CMRAA private business that receives mail as an agent for specific clients.
PBSAA Post Office Box Street Address.
VacantA delivery point that was active but is vacant, in most cases unoccupied over 90 days, and not receiving delivery.
SeasonalA delivery point that may receive mail only during a specific season.
EducationalA college, dormitory, sorority or fraternity house, or apartment building occupied mostly by students.
No-StatAn address not receiving delivery and not counted as a possible delivery.
DropA single receptacle or drop site that serves several dwellings, businesses or addresses.
Drop countThe number of customers sharing the receptacle.
PO Box ThrowbackA street address whose mail is delivered to the customer's PO Box.
LACSAn address converted from rural style to city style because of 911 systems.
Door Not AccessibleAn address where the carrier cannot knock on the door or reach the building.
No Secure LocationAn address with no secure place for delivery.
Non-delivery daysAn address that gets no mail on at least one day of the week.

Each record also carries a delivery type code.

CodeDelivery typeWhat it means
1CurbA receptacle at the curb, served from a vehicle.
2NDCBUA receptacle inside a cluster box.
3CentralA receptacle inside a centralized unit, such as a gang box.
4Door slotDelivery through a door slot.

A No-Stat record also carries a reason code that says why it is not counted.

ReasonWhat it means
1An internal drop address, delivered through a drop address that serves it.
2An address that has not yet become deliverable.
3A collision: an address that does not actually DPV confirm.
4College, military and other ZIP + 4 records USPS has added to the data.
5A regular No-Stat, not receiving delivery and not counted as a possible delivery.
6An address that requires secondary information.

Business, residential or unknown

A record that is not a business is either unknown or residential. Both kinds have a DPV/DSF2 confirmation indicator of Y and are not in the Business table. An unknown record has a blank delivery type, and a residential record does not.

TestResidentialUnknown
DPV/DSF2 confirmation indicatorYY
In the Business tableNoNo
In the No-Stat tableNoMay be
General DeliveryNoNot stated
Delivery typeNot blankBlank

Reports

A licensee captures processing statistics during every run. It collects the files from all runs and sends them to USPS monthly. Each customer gets a customer number, a unique six-digit numeric or alphanumeric value. Online inquiries are counted apart from batch processing, as one record per customer each month.

The monthly file is named [Licensee Number][mmyy].dat, such as 12340201.dat. It goes to the National Customer Support Center in Memphis, TN, within seven calendar days of the month. The licensee keeps the reports for five years for Postal Service review.

Becoming a licensee

An applicant must obtain CASS certification for ZIP + 4 processing before DSF2 licensing. The certification steps must be submitted in sequence. Submitting all steps at once is prohibited.

  1. Submit the application and self-certification statement for USPS approval.
  2. On approval, receive the Interface Developer Guide and the Stage I files.
  3. Submit the technical proposal, security documentation, key personnel form and equipment information.
  4. Build the interface and submit a completed test run with its required data.
  5. Once that run is approved, request the DSF2/CASS certification test in writing.
  6. Process the USPS test file, including finding the DPV Stop Processing seed address.
  7. Sign the license agreement and return it to USPS with the payment.

An officer with legal authority to sign for the organization signs the agreement. USPS then grants access to the monthly product updates through Electronic Product Fulfillment.

Testing requires 100 percent accuracy on the DSF2 elements of each test address the applicant's CASS process codes correctly. USPS can also test a licensee's DSF2 process at any time without advance notice.

Rules

In accordance with the License Agreement between USPS and Licensee, DSF2 shall be used to identify legitimately obtained addresses only, and shall not be used for the purpose of artificially creating address lists.

DSF2 must be used only on addresses obtained legitimately. It must not be used to create address lists.

A Licensee or software developer writing an interface to DSF2 tables must first ensure the address list is processed through USPS CASS Certified software to obtain a 9-digit ZIP Code™ and a parsed address immediately prior to the DSF2 process.

The list must go through CASS Certified software right before DSF2, to get a 9-digit ZIP Code and a parsed address.

No online inquiry system, regardless of inquiry origination, shall provide the extended address attributes listed in Exhibit I.

An online lookup system must not return the extended address attributes, whoever sends the inquiry.

USPS-supplied DSF2 updates more than 60 days old shall be destroyed using common practice for disposal of sensitive materials, such as permanent file deletion.

A licensee must destroy any DSF2 update more than 60 days old, for example by deleting the file permanently.

DSF2 Licensed Service providers must perform at least 51 percent of their list processing on behalf of commercial customers and must limit processing of their own lists to no more than 49 percent of the total usage.

A licensee must do at least 51 percent of its list processing for commercial customers. Its own lists must be no more than 49 percent of its total usage.

The Licensee shall not export the DSF2 product outside the boundaries of the United States of America or its territories.

A licensee must not take the DSF2 product outside the United States or its territories.

If the customer’s list is being processed for walk-sequence information, the Licensee must use eLOT service to get the walk sequence number.

When a list is processed for walk sequence, the licensee must get the walk sequence number from eLOT.

The Licensee must process and return all customer mailing address list files within seven (7) business days of receipt unless a longer period is specified by the customer in writing.

A licensee must return each customer list within seven business days, unless the customer sets a longer period in writing.

What goes wrong

The False Positive table holds addresses USPS manufactured to catch lists that were not obtained legitimately. When a list matches that table, the licensee may keep processing but must notify USPS of the customer's name and address at once. It sends a file of the affected addresses to Dsf2stop@usps.gov with the subject line DSF2 False Positive. Every document the customer gets about the match must carry USPS's explanation of the stop processing function.

USPS can require a licensee to suspend a customer's processing after repeated detections of artificial addresses. A list whose ZIP + 4 matches and DSF2 matches differ by 49 percent or more is also reported to Dsf2stop@usps.gov. Processing does not stop for that report. The licensee keeps every false positive report for five years.

A DSF2 interface stops working once its data is more than 60 days past the product date. When USPS finds a problem in a licensee's DSF2 process, it may direct a fix, suspend the license or end it. Inaccurate information given to USPS can get a license suspended at once, until accurate documentation is approved.

Terms

walk sequence
The order in which a carrier delivers mail for a route. This order is required for most carrier route presort mail.
simplified address
An alternative addressing format used when delivery of identical mail is requested to every customer on a rural route or highway contract route, or to all Post Office Box customers at a Post Office without city carrier service. Instead of listing the addressee’s name and address, the mailer may use “Postal Customer." The format may also be used for certain types of mailpieces on a city route and to Post Office Boxes in offices with city delivery service when a complete distribution is made to each active residential delivery or each active delivery on the route or to the box section. Government agencies may also use this format for official mail sent to all stops on city routes and Post Office Boxes at Post Offices with city delivery service. In such cases, these formats may be used: “Postal Customer,” “Residential Customer,” and “Business Customer,” depending on the coverage type requested.
Enhanced Line of TraveleLOT, eLine-Of-Travel
The eLOT product allows mailers the ability to sort their mailings in approximate carrier-casing sequence.
Delivery Statistics ProductDelivery Statistics
The Delivery Statistics Product defines the number of post office boxes and business/residential deliveries on city, rural, and highway contract routes for every ZIP Code™ in the United States.
Electronic Product FulfillmentEPF, Electronic Product Fulfillment (EPF) web site, Electronic Fulfillment Website
A secure web-based application managed by the National Customer Support Center in Memphis TN that is used to post and receive Address Management and Address Information System products, including ACS fulfillment files.
ZIP+4ZIP+4 CODE
An enhancement to the 5-digit ZIP Code that uses an additional four digits to represent the sector (a geographic area or neighborhood) and segment (a smaller unit such as a building, floor, street block) for an address within a 5-digit zone.
Commercial Mail Receiving AgencyCMRA, commercial mail receiving agencies, Commercial Mail Receiving Agent
A private business that provides mail delivery service to individuals or business that rent Private Mail Boxes (PMB) through them.
vacant delivery point
A delivery point that was active in the past but is currently not occupied (generally not occupied for 90 days or more) and not receiving mail delivery. It does not include businesses or homes under construction, demolished, or otherwise identified as unlikely to become active.
no-stat delivery point
A business or dwelling under construction, demolished, blighted or otherwise identified as not likely to become active for some time, or a rural route address that has not been receiving mail for 90 days or longer. No-stat and vacant tables are part of the Delivery Point Validation product.
PO Box Throwback
Denotes the address associated with this delivery point is a street address; however the delivery is made to the customer’s PO Box address.
Door Not AccessibleDNA
Addresses where carriers cannot knock on the door for mail delivery or where carriers cannot physically access a residence/building, such as rural/highway contact route (HCR) long driveway or gated community.
Undeliverable as AddressedUAA, UAA mail
mail that the USPS cannot deliver as addressed and must be forwarded to the addressee, returned to the sender, or discarded depending on the authorized treatment for that mail class and/or specific instructions provided by the mailer through ancillary service requests

Documents

Tech Guides

User Guides

Quick Service Guides

Fact Sheets

Contact Lists

Data Files

Release Notes

Applications/Forms

Contacts

  • Licensing and certification questions: the Move Update Support Department, 1-800-589-5766.
  • Certification submissions: DSF2 Department, United States Postal Service, 225 N Humphreys Blvd Ste 501, Memphis TN 38188-1001.
  • False positive and match-difference reports: Dsf2stop@usps.gov.
  • Monthly statistics reports: the National Customer Support Center, Memphis, TN.

Sources