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May 14, 2021

What is CASS Certification?

CASS, (the Coding Accuracy Support System) is a voluntary certification system provided by the United States Postal Service for mail services providers. CASS certification means that a service or application works correctly with the internal USPS systems within the United States. This certification helps everyone involved in mailing, reducing workload and lost letters for USPS, providing advertising and discounts for certified providers, and helping businesses rule out unreliable providers. 

Why Does the USPS Provide CASS Certification?

CASS Certification is a testing and certification process that allows USPS to grade the accuracy of address verification tools. By using a standardized testing and certification process, USPS is able to ensure they can deliver mail successfully and efficiently and provides businesses another data point when evaluating vendors. This works in three principle ways: 

  • Making sure addresses are accurate and deliverable
  • Including all 9 digits of the ZIP Code™ (also known as the Zip + 4)
  • Including other mailing information that helps USPS

Accuracy and deliverability

USPS CASS Certification ensures that a provider’s mailing tools work with the USPS’ Address Matching System. The tools that CASS Certified providers need to support include:

  • DPV®: Delivery Point Validation confirms the accuracy of an address. It checks addresses to confirm that they exist, and the USPS is able to deliver to them.
  • LACSLink® is a system created for, and maintained by the 911 service in order to help emergency responders arrive quickly at the correct location. For the USPS, It helps eliminate duplicate mail and ensures mailings are addressed correctly, primarily by updating rural addresses (often with a “Route” and Box number) with modern, city-style addresses using a street name, number and number. It also keeps current records when city addresses are renamed.
  • SuiteLink®: This business-oriented service helps with delivery to organizations in highrise buildings. SuiteLink is used to add the Suite number or other secondary information to business addresses in high rises, assuring that mail arrives at the correct office.
  • Carrier Routes: A carrier route is a group of about 15 addresses within a particular Zip Code. Carrier routes are a system the USPS uses to help plan and execute effective mail routes for carriers, enabling them to quickly and efficiently deliver mail. 

ZIP + 4

The ZIP Code is a series of numbers used to specify where an address is located, and provide details about the specific location, making it quicker and easier for mail carriers to deliver mail successfully. As the USPS explains, the first five numbers give the“sectional center” or city, along with the local “delivery area” or post office where the letter is being sent. 

The last four digits further specify the location, down to a single side of a street. Some organizations, such as government agencies or companies that receive a lot of mail, are also assigned unique zip codes.

Including ZIP + 4 is just one more way to reduce the workload for USPS, and reduce the number of undeliverable letters.

Helping the USPS deliver mail

CASS Certified software encodes mail with information that goes beyond standard address information, to make it quicker and easier to deliver mail. For example, business mail will be encoded with a Delivery Point Barcode (DPBC) — a numerical code that the USPS can use to automatically sort mail for delivery. The DPBC encodes the ZIP + 4, along with a two digit code and a check digit. When addresses have multiple apartments, suites or offices, the two digits help ensure that each piece of mail goes to the right location. 

How Will CASS Certified Mail Software Help My Company?

CASS Certified direct mail makes it easy to keep your address list accurate and up-to-date. Lob’s address verification software empowers you to quickly and easily check any address in the United States, to ensure that it is accurate, up-to-date, and correctly formatted. This software can be integrated with your direct mail workflow, ensuring your contact information stays accurate when contacts move or locations receive new addresses.

CASS Certified providers can also save you money in a couple ways. By standardizing address formats and eliminating duplicate and incorrect addresses, you’ll avoid wasting money on undeliverable or redundant letters and mailings. Additionally, you can benefit from the discounted rates your provider receives, further cutting direct mail spend.

Is CASS Certification Enough?

CASS Certification guarantees a standard of quality in direct mail services and platforms, but it doesn’t guarantee an extensive range of services. It’s a good tool to rule out low-quality vendors, but you still have to look at what capabilities a particular provider brings to the table. 

Choosing a CASS Certified provider is a bit like finding a contractor to work on your house. Looking exclusively at licensed and bonded contractors will help you eliminate unqualified candidates, but you still need to look at the range of services, expertise and cost each contractor offers.

Here are a few of the capabilities you should look for in a CASS Certified vendor

End-to-end services

For most companies, handling printing and sending direct mail internally is costly and wasteful. While you can outsource these tasks to different vendors, that can pose its own problems, including a complex workflow, delays, and added vendor management duties.

By obtaining all your direct mail and address verification services from a single vendor, you can plug straight into a streamlined, cost-effective workflow, saving money and accelerating your cadence. Check out our ebook on Modernizing the Direct Mail Process to learn more.

Print customization

Most companies have little to no capability to customize their direct mail. That makes it very difficult to target customers, partners and leads with content that’s relevant to them, limiting the effectiveness of your direct mail campaigns. 

Look for a vendor that allows you to customize text and images on all your mailings, while providing a range of out-of-the-box form factors. 

Templating functionality

Templates enable you to create merge variables, which can be filled in with custom content designed for each recipient. This enables you to effectively use print customization, and empowers your marketing team to get much more granular with targeting. 

Lob provides built-in templating capabilities, with an extensive template gallery and unlimited freedom to customize your templates to meet your organization’s communication needs. This capability comes integrated with our services, giving you a high degree of customizability from day one.

Omnichannel capabilities

Direct mail is just one of many channels your company uses to communicate. To be effective, your organization needs to be able to coordinate its message across all channels, with a consistent workflow and shared analytics. 

Choose a direct mail platform that integrates seamlessly with your existing marketing and transactional platforms. This will enable your team to combine direct mail with email, social media marketing, SMS and other channels into a single communication strategy. 

Bulk Discounts Regardless of Volume

Many companies negotiate their mailing costs on a per-campaign basis. While this can provide cost savings on large bulk mailings, smaller, more targeted campaigns still remain costly and in many cases, impractical. 

Look for a CASS Certified provider who can bundle your direct mail with other clients, regardless of the volume. Not only will this keep your costs low — it will also eliminate the extra work and delays imposed by negotiating each campaign. 

More Than CASS Certified Direct Mail 

There are a number of organizations that can boast of CASS Certification, but when it comes to providing a complete direct mail solution, there’s really only one choice. Lob leads the pack, with complete, end-to-end direct mail services, with the quality and reliability of CASS certification. 

Contact us to learn how Lob can modernize your direct mail program, providing the flexibility, reliability and low cost of a digital channel at the mailbox. 


This blog provides general information and discussion about direct mail marketing and related subjects. The content provided in this blog ("Content”), should not be construed as and is not intended to constitute financial, legal or tax advice. You should seek the advice of professionals prior to acting upon any information contained in the Content. All Content is provided strictly “as is” and we make no warranty or representation of any kind regarding the Content.

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