What Is CASS? How Postalytics Uses USPS Address Validation to Deliver Smarter Direct Mail

In the world of direct mail, accuracy is everything. Every misdirected postcard or undeliverable letter doesn’t just waste budget—it erodes trust, reduces ROI, and leaves marketing teams in the dark. That’s where CASS comes in.

At Postalytics, we use the USPS CASS system to ensure that your mail only goes to real, deliverable addresses—and we don’t stop there. With built-in automation, real-time visibility, and measurable savings, we’re turning what was once a tedious manual process into a powerful, budget-friendly asset.

So, what is CASS—and how do we turn it into real value for marketers?

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What Is CASS?

CASS stands for the Coding Accuracy Support System, a certification program developed by the United States Postal Service (USPS). Its purpose is to evaluate and improve the accuracy of address-matching software used by mailers and service providers.

CASS-certified software performs three core tasks:

• Standardizes mailing addresses to USPS format
• Corrects address errors like misspellings or incomplete ZIP codes
• Validates addresses to confirm they actually exist and can receive mail

This system ensures that mail is deliverable, formatted correctly, and optimized for postal discounts. It’s essential for any high-performance direct mail strategy—and it’s fully integrated into every Postalytics campaign.

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How Postalytics Utilizes CASS for Address Accuracy

When you upload a contact list or trigger a contact for mailing into Postalytics, it’s processed by our CASS-certified engines prior to mailing. Here’s what happens behind the scenes:

1. Standardization

Postalytics reformats every address to meet USPS guidelines. For example, “123 main st apartment 4b” becomes “123 MAIN ST APT 4B.” This ensures consistency across your data and lays the groundwork for reliable deliverability and suppression list matching.

2. Correction

If there are obvious mistakes in your list—like “15 Boxton Rd” instead of “15 Boston Rd”—CASS catches and corrects them. Our system also fills in missing data like ZIP+4 codes when possible.

3. Validation

Postalytics checks each address against USPS records to confirm it actually exists and is deliverable. If an address doesn’t pass validation, we flag it—and you won’t pay to mail to it.

This process all happens in seconds, automatically. No manual data cleanup. No third-party coordination. Just clean, validated lists every time you send.

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Saving You Money: Credits for Undeliverable Addresses

Here’s where we go beyond just protecting your deliverability—Postalytics protects your budget, too.

Whenever CASS determines that an address is undeliverable, Postalytics issues a credit for that piece. That means you don’t pay for printing, postage, or fulfillment on mail that’s guaranteed to fail.

Our address validation process helps you:

• Avoid spending on undeliverable mail
• Improve campaign ROI
• Optimize your contact lists for future sends

With Postalytics, there’s no guesswork. You know exactly how many addresses were filtered out—and exactly how much money you saved.

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Enhancing Suppression Lists with CASS

Postalytics’ suppression list capabilities allow you to block specific contacts, customer types, ZIP codes, or other segments from receiving future mailings. This is critical for avoiding duplicate mailings, respecting opt-outs, and managing marketing fatigue.

Here’s the catch: suppression lists only work when the addresses match exactly. That’s where CASS makes a major difference.

Because Postalytics standardizes all addresses during CASS processing, we eliminate formatting inconsistencies that would otherwise cause suppression mismatches. Whether someone inputs “Ste” or “Suite,” or “Ave” vs “Avenue,” our system sees them as the same—so suppressions stick.

Learn more about how to use suppression lists effectively.

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Real-World Results: Goodman Manufacturing’s Success with Postalytics and CASS

Goodman Manufacturing, a division of Daikin Comfort Technologies, faced a common marketing challenge: direct mail campaigns that were inefficient, expensive, and plagued by questionable data quality.

Using Postalytics, Goodman saw a major turnaround:

• Data Accuracy: CASS validation helped Goodman eliminate duplicates and undeliverable addresses, refining their U.S. mailing list to a verified 33,000 contacts. That’s thousands of wasted mailings prevented—and thousands of dollars saved.
• Self-Service Speed: Instead of relying on third-party vendors, Goodman’s team handled creative, uploads, and sending directly in the Postalytics platform. “We found it was much easier to create the graphics and then upload them ourselves,” noted Tanya Steindl, Director of Marketing.
• Tracking and Insights: Postalytics’ dashboard gave them visibility into which addresses were deliverable, how mail performed across regions, and how to iterate for better results.
• Budget Impact: “Now we know our list is around 33,000 names. We had believed it to be larger, and we were paying the third parties for more work than was necessary,” said Steindl.

For Goodman, CASS wasn’t just a backend process—it was the foundation for smarter strategy and measurable ROI.

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See the Savings: Real ROI with the Mail Address Savings Analysis Tool

Want to see how CASS translates to real-dollar savings? Postalytics customers on the Marketer, Pro, and Agency plans have access to the Mail Address Savings Analysis tool—a dashboard that shows you exactly how much money you’re saving thanks to address validation.

You’ll see:

• How many undeliverable addresses were removed from your campaigns
• How much credit you earned back from those removed pieces
• Your total savings over time

For high-volume senders, this can add up to thousands in reclaimed marketing spend. It’s data you can show to your team, your CFO, or your clients—because it proves that clean data pays off.

Explore the tool in action: Mail Address Tool Savings Now Live

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Tips for Optimizing Your Mailing Lists

To maximize the impact of CASS validation in Postalytics:

• Always provide complete address info: Include street, city, state, and ZIP.
• Avoid placeholder data: Entries like “N/A” or “TBD” will be flagged.
• Use clean CSV formats: Although we clean addresses for you, proper formatting helps speed processing.
• Check your dashboard: Our campaign dashboards show CASS errors, address statuses, and credits applied—so you’re always in the loop.

Need a refresher? Visit our file preparation guide and dashboard definitions.

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Conclusion: What Is CASS? It’s Your Direct Mail ROI Engine

CASS isn’t just an acronym—it’s the difference between sending smarter and sending blind. By standardizing, correcting, and validating addresses, the USPS CASS system ensures your mail gets where it’s supposed to go—and with Postalytics, it’s fully automated, measurable, and built into every campaign.

Best of all? You only pay to send to valid, deliverable addresses. Every filtered record is money saved and performance improved.

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