CASS. Standardize
before USPS rejects.
Every USPS address has a canonical format defined in Publication 28 — abbreviated suffixes, normalized apartment notation, validated ZIP+4 with a 2-digit delivery point code. CASS, the Coding Accuracy Support System, is the USPS-certified process that standardizes every address on a list to that format and confirms a real delivery point exists at the result. Skip CASS and the drop loses its automation postage discount and the throughput advantage that comes with it. DirectMail.io runs CASS in the same pre-flight pass as NCOA, on every list, every drop.
Five steps. Set up zero. Runs per drop.
- 01
List enters the same hygiene pass as NCOA
CASS does not run on its own. It runs in sequence on the same pre-flight pass that handles NCOA, suppression, and deduplication. One pass, one report, one pass/fail per record.
- 02
Address parsing and Pub 28 normalization
Each record is parsed into its components — number, street, suffix, unit, city, state, ZIP — then normalized to USPS Publication 28 format. "Street" becomes "ST," "Apartment" becomes "APT," casing standardizes, ambiguous suffixes resolve.
- 03
AMS database match for ZIP+4 and delivery point
The normalized address is matched against the USPS Address Management System (AMS) database. A successful match returns the ZIP+4 code and a 2-digit delivery point code (DPC) — the building-level identifiers USPS sortation needs to qualify the piece for automation.
- 04
DPV validates the delivery point exists
Delivery Point Validation confirms the address corresponds to a real, deliverable mailbox. CASS confirms the format is right; DPV confirms a real delivery point matches. Records that fail DPV are most often typos or non-existent units, surfaced in the rejection report.
- 05
CASS certification rides with the manifest
The output is a CASS-certified address record USPS sortation can read at automation rates. The certification stamps the manifest the platform produces — no separate filing, no paperwork, no "did the vendor remember to do this" question at intake.
Why the rate hit is the small problem.
USPS sorts well over a hundred billion mailpieces a year, and the entire automation infrastructure assumes the address on the piece matches the format the sortation reads. A non-CASS’d address — even one a human can read perfectly — gets pulled out of automation and handled by hand. The per-piece postage rate jumps. Sometimes the piece is rejected back to the sender for a corrected address.
The bigger cost isn’t the postage hit. It’s the throughput. A drop that doesn’t qualify for automation can sit at the postal facility for days while the manual sort gets to it. Co-landed email triggers, response-window timing, and ROI calculations all depend on USPS hitting the planned in-home date. CASS is the precondition that lets that happen.
CASS-certified software is recertified by USPS annually, and out-of-date CASS processing is one of the more common — and most avoidable — reasons drops get pulled from automation at intake. DirectMail.io maintains current certification. Every drop the platform produces runs on the CASS version USPS infrastructure expects to see.
Where CASS earns its keep.
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Lists from third-party data partners
Raw consumer or B2B data arrives in inconsistent formats — abbreviations, casing, suffix variants. CASS normalizes everything to USPS standard before a single piece composes for print.
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B2B drops with suite and floor numbers
Commercial addresses live or die on apartment and suite notation. CASS standardizes the unit segment; DPV confirms the suite actually exists at the building. Misrouted mail to commercial buildings rarely recovers.
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Re-prospecting against an existing CRM
Addresses captured at signup drift over years — typos, apartment-number changes, ZIP code splits. CASS on every drop catches the drift before the postage gets paid on a record USPS cannot place.
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High-volume drops where every basis point matters
At volume, the per-piece automation discount differential compounds into meaningful margin. CASS-clean records hitting automation rates is often the difference between a profitable program and a break-even one.
Questions teams ask before deploying.
Short answers. For implementation specifics on your stack — custom parsing rules, B2B suite handling, audit reporting — book a demo.
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What is CASS and what does it stand for?
CASS stands for Coding Accuracy Support System. It is the USPS-certified process that standardizes every address on a mailing list to the format defined in USPS Publication 28 — abbreviated street suffixes, normalized apartment notation, validated city and state combinations — and appends the ZIP+4 code and a 2-digit delivery point code to each record. CASS is the precondition for USPS automation postage discounts on First-Class Mail and USPS Marketing Mail.
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How is CASS different from NCOA?
NCOA updates the address based on whether the recipient moved. CASS standardizes the format and validates that the address itself is real. They run in sequence on every list — NCOA decides which address goes on the piece, CASS confirms that address is in the format USPS sortation needs to read it. A list with NCOA but no CASS still loses automation discounts. A list with CASS but no NCOA sends a cleanly-formatted piece to someone who no longer lives there. DirectMail.io runs both as a single pre-flight pass on every drop.
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What does DPV actually check?
DPV stands for Delivery Point Validation. It confirms the address corresponds to a real, deliverable location — a specific mailbox USPS will actually deliver to. CASS gets the format right; DPV confirms the mailbox exists. A CASS-clean address that fails DPV is most often a typo (for example, "123 Maon St" where "Main" was meant) or a non-existent unit number on a real building. DPV runs as part of every CASS pass in DirectMail.io, and the failures are reported back per record.
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Is CASS certification required for automation postage rates?
Yes. The USPS Domestic Mail Manual requires CASS-certified processing for any drop claiming automation rates on First-Class Mail or USPS Marketing Mail. Without it, the drop pays a higher per-piece postage rate and gets handled outside the automation infrastructure. The discount differential per piece is small at first glance, but at high volumes it represents a meaningful share of total postage spend — and the speed-of-delivery hit from non-automation handling is often the bigger operational cost.
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How often is CASS-certified software recertified?
Annually. USPS issues a recertification cycle each year, and any CASS-certified software vendor must pass it to remain certified. DirectMail.io maintains current CASS certification — every drop runs on the version USPS infrastructure expects to receive. Out-of-date CASS software is one of the more common (and avoidable) reasons drops get pulled from automation at intake by the postal facility.
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What happens to records that fail CASS or DPV?
They are reported back, not silently dropped. The DirectMail.io dashboard surfaces the failure reason per record — no ZIP+4 match, DPV miss, ambiguous parse, multiple-unit conflict — so the team can investigate the data source. Failed records can be manually reviewed, suppressed from the drop, or sent back to the data partner for correction. Nothing is silently mailed and nothing is silently lost.
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Does DirectMail.io run CASS automatically?
Yes. Every list — uploaded, SFTP-pushed, API-pushed, or appended through the data layer — runs through CASS as part of the standard pre-flight hygiene pass. There is no "skip CASS" toggle on production drops. The certification rides with the manifest USPS receives, so the drop is automation-qualified at intake without any additional filing or paperwork from the team.
Run CASS on your next drop.
30-minute demo. We’ll process a sample of your list, show the standardized output and DPV validation report, and walk through the automation-postage qualification documentation USPS receives with the manifest.