USPS Undeliverable Mail Reasons and Prevention

Introduction

In an ideal world, once you send documents to your customers, clients, or patients, the printing and mailing process is mostly done. You can be relieved that your communications will get to where they need to be on time, in accordance with compliance requirements, and you can move onto other pressing tasks.

Which is why, if you see that same mailpiece returned to you with the marking “undeliverable as addressed,” it can feel dejecting. Now, not only do you have to put this mailpiece through your mailing workflow again, but you have to spend time determining why your USPS mail didn’t get where it needed to be and correcting the problem.

Almost 2 billion pieces of First-Class Mail were marked “undeliverable as addressed” during Fiscal Year 2024. Most of these mailpieces were returned to sender, while some were able to be forwarded and others were treated as waste. Undeliverable mail is a common concern for those needing to print high volumes of documents, and this blog post can help you address it.

This article breaks down common USPS undeliverable mail reasons, so you can get a better sense of what leads to these types of problems. We’ll then move onto what happens when mail can’t be delivered, and how organizations that need to send high volumes of documents can prevent the causes of undeliverable mail.

Key Takeaways

• Common USPS undeliverable mail reasons include poor address quality, the recipient having moved, and delivery access problems.

• The USPS processes billions of undeliverable mailpieces each year, costing both the Postal Service and mailers billions of dollars in wasted postage, materials, and labor.

• Many of the most common issues that lead to undeliverable mail can be solved by fixing the data quality of customer databases.

• Preventing the causes of undeliverable mail improves delivery efficiency, lowers operational costs, and protects compliance in regulated mailing workflows.

• High-volume mailers can reduce undeliverable rates by using automated data cleansing software and USPS-approved address verification tools.

• D4 Solutions uses its experience in printing and mailing for highly regulated industries to ensure accuracy of addresses and deliverability of mail.

What Is Undeliverable Mail?

Any mailpiece that cannot be delivered to the name and address listed on the envelope or label is undeliverable. This classification doesn’t necessarily mean the address doesn’t exist. It simply indicates that, based on available data and delivery conditions, there’s a reason that this item can’t reach its intended recipient through normal delivery channels.

Mail can become undeliverable for temporary or permanent reasons. A temporary issue might involve a closed business, inaccessible mailbox, or a recipient who’s away but has no forwarding order. A permanent issue often stems from invalid address data or from the intended recipient having moved.

Undeliverable mail follows specific USPS handling procedures determined by mail class and by any special service endorsements applied by the sender. First-Class Mail is typically returned to the sender at no extra charge, and Marketing Mail may be discarded if no forwarding or return instructions are included.

Common USPS Undeliverable Mail Reasons

The USPS handles more than 100 billion mailpieces annually, and a significant portion never makes it to the intended address for one cause or another. The agency groups these mailpieces into several categories based on what prevented delivery.

Below are some of the most common USPS undeliverable mail reasons, how they arise, and what can be done before production or dispatch to ensure all mail gets to where it needs to go:

Recipient Has Moved

This is one of the most common causes for USPS mail to be undeliverable. If one of your intended recipients has moved without an active forwarding order, that is a reason that USPS mail can’t be delivered to them. USPS forwarding services for First-Class Mail cover moves for a defined period. Usually that period lasts 12 months, but consumers can pay for it to last an additional 6, 12, or 18 more months. After the forwarding period ends, USPS returns the mail to sender with the new address, and after that, items sent to an old address are flagged as undeliverable, and are returned to sender with reason for nondelivery.

The USPS NCOA database is the primary safeguard against this issue. It stores move data submitted by households and businesses that file forwarding requests. Mailers who regularly process address lists through NCOA matching can automatically update many of their records before mailing.

NCOA will significantly help reduce your volume of documents that are unable to be delivered by USPS, but it won’t entirely solve the problem. Some recipients never file an official address change, or they leave gaps by moving multiple times in quick succession. Business addresses also might change ownership or tenancy without forwarding, leaving outdated suite information in circulation.

Still, NCOA is the tool that best counteracts this reason for USPS undeliverable mail. You or your outsource mailing partner should run NCOA checks at least once every 95 days and update your mailings accordingly. There’s a reason why doing so is required by the USPS to obtain the largest postal discounts for your mail.  It’s also smart to design mailings with address automation systems that track returning mailpieces. You should and code USPS undeliverable mail, and analyze this mail for recurring patterns.

Address Quality Errors

Address inaccuracy is another common reason for USPS undeliverable mail. Typos, missing secondary designators like apartment and suite numbers, transposed zip codes, and poorly formatted entries all cause failures in mail automation systems that may prevent the USPS from reading the address on the envelope.

Inconsistent database standards across departments can introduce errors when records are merged or exported for mailing. Mistakes in data entry, error on customer provided forms, and outdated system integrations are other potential causes of USPS undeliverable mail.

Address quality errors can be prevented with the use of CASS-certified address validation software to ensure that data is accurate and follows USPS specifications. Regular database audits and regular NCOA updates also help mailpieces make it to their intended destination.

Refused or Unclaimed Mail

Refused and unclaimed mailpieces reach their destinations but are not accepted by their intended recipients. When the customer actively rejects a delivery, that mailpiece is refused. Unclaimed mail sits at a receptacle, such as a post office or a mailbox, but is never picked up.

Both cases are causes of USPS undeliverable mail. They also may act as signals that your customers are not engaged with your business.

To prevent certified or time-sensitive mail routinely going unclaimed, review your communication methods with your customers. Keeping recipients are aware of what mail you’re going to send them can lower refusal rates.

Deceased Recipients

The USPS identifies mail addressed to deceased recipients through internal records, public data, and manual notifications from family members. Mail sent to a deceased recipient is returned to sender unless an authorized representative has filed forwarding instructions.

Incorporating deceased suppression files into your mailing workflow can prevent this cause of USPS undeliverable mail. These databases regularly cross-reference national death records to remove affected individuals before mail is sent.

Delivery Access Problems

Physical and logistical barriers can sometimes make delivery of correctly addressed mailpieces impossible. Locked gates, inaccessible delivery points, severe weather events, and unsafe property conditions are all reasons that prevent USPS mail from reaching its intended destination.

Maintaining updated contact records for recipients can help you identify the root causes of undeliverable USPS mail. If mail is frequently returned from a specific location, USPS route data or local post office feedback can reveal whether physical access is the issue.

Undeliverable mail leads to increased reprints and to increased postage costs from these reprints. It also diverts staff time away from other activities in order to handle the returned envelopes. It can even affect compliance by delaying critical communications like statements or legal correspondence, which is why preventing the causes of undelivered mail is highly beneficial.

What Happens to Undeliverable Mail Once Its Cause Is Identified

When a mailpiece cannot be delivered, it is either forwarded, returned, or disposed of. The process of handling undeliverable mail varies based on mail class, service endorsements, and the specific reason that USPS delivery failed.

If the recipient has filed a valid forwarding order and the mail class allows it, USPS readdresses and routes the item to the new address. This process is automatic for First-Class Mail and certain Parcel services, though forwarding timeframes depend on recipient filing accuracy.

Mail that cannot be forwarded or matched to a forwarding record is typically returned to the sender, provided it bears a valid return address and the mail class includes return privileges. First-Class Mail and Priority Mail are always returned. Marketing Mail, however, is not automatically returned unless the sender included an explicit endorsement such as “Return Service Requested” or “Change Service Requested.” Without that direction, USPS is authorized to dispose of the item after processing.

How to Prevent the Causes of Undeliverable Mail in High-Volume Operations

If you’re handling large and data-driven mailings, then preventing the causes of USPS undeliverable mail helps you better reach your customers. It keeps time-sensitive mailings compliant, and getting documents to your consumers when you say you will helps your organization maintain consumer trust.

Here are some steps you can take to prevent the sending of USPS undeliverable mail:

Maintain a Clean and Standardized Address Database

Very frequently, the reason mail does not arrive at its destination is weak data hygiene. Addresses might lack consistent formatting and validation when they’re collected from multiple different databases. If these errors are not corrected, they might cause USPS automation to reject or misroute mail.

Conducting routine address verification is a simple solution to this problem. Coding Accuracy Support System (CASS) software helps every record adhere to USPS formatting. The NCOA is a secure database of 160 million permanent change-of-address records that have been filed with the USPS, and regularly cleansing data against this database helps prevent mail from going to outdated addresses. Regularly running checks with CASS software and the NCOA database keeps mailing lists aligned with USPS data and helps prevent a key cause of undeliverable mail.

Use Pre-Processing Validation Before Printing

Pre-processing validation helps detect null fields, incorrect zip codes, and other causes of undeliverable mail. Pre-processing validation techniques automatically identify issues and flag discrepancies for review, preventing incorrectly addressed mail from entering the mailstream.

Use The Right USPS Ancillary Service Endorsement

How undeliverable mail is handled after it leaves your facility depends on which endorsements are applied. USPS offers several standardized ancillary service endorsements that dictate whether items are returned, forwarded, or disposed of. Here are common endorsement categories, so you can choose which one is right for your mail:

• Return Service Requested: Undeliverable mail is returned to the sender. If the USPS has updated address information, it is attached to the mailpiece, and if not, the reason for non-delivery is attached.

• Address Service Requested: Mail is forwarded if the recipient has provided a new forwarding address and mail is sent within the right timeframe. Undeliverable mail sent within 12 months of a move is forwarded, and mail sent between 13 and 18 months after a move is returned to sender with the new address attached. Mail sent 18 months or more after a move, or undeliverable mail sent to a recipient that has not provided a forwarding address, is returned with reason for non-delivery attached. If mail is forwarded, information about the recipient’s new address is delivered to the original sender, usually at a fee.

• Forwarding Service Requested: Handled the same as Address Service Requested, except, if the mail is successfully forwarded, no information about the recipient’s address is sent to the original mailer.

Using the right endorsement type helps you update your records if your mail is sent to an undeliverable address.

Implement Quality Control During Production

Poor print quality and mechanical issues can cause mail to be undeliverable. Production workflows should implement procedures to avoid this. Mailers should regularly calibrate print devices and verification scanners, and they should include automated inspection systems that read and verify barcodes. These checks allow all mail to meet USPS standards before it enters distribution.

Monitor Return Data and Trends

Returned mail is a source of valuable diagnostic information. Tracking the amount of undeliverable mailpieces and their return codes can reveal recurring issues. If there are specific zip codes with frequent rejections, or particular mail types generating higher refusal rates, these issues can be identified by analyzing patterns in returned mail. After finding potential problems, operations teams should correct source records and update address logic.

Build Strategic Partnerships with Print and Mail Providers

Outsourcing partners can add another layer of protection against the causes of USPS undeliverable mail. Leading providers use certified address databases to prevent delivery errors and barcode tracking to respond to issues. This helps reduce the volume of undeliverable mailpieces and also helps maintain audit trails, which are important in any environment where compliance is a key concern.

Most causes of undeliverable mail are preventable with disciplined address management and production controls. USPS processes can only work with the information they are given, and when that information is incomplete or outdated, mail won’t get to where it needs to be. Verification and database hygiene tools can help organizations minimize returns, cut waste, manage more reliable physical communication channels, and maintain customer reputation.

D4 Solutions: Your Secure and Reliable Print and Mail Services Provider

In-house mail operations present logistical challenges that are outside of many organizations’ areas of focus. Professional print mail service providers like D4 Solutions handle everything for you, including preventing the causes of USPS undeliverable mail and resending any mail that does not arrive as intended.

We have a deep experience handling confidential and highly-regulated materials such as billing statements, tax forms, and policy documents. Address errors while sending these forms are unacceptable, and we know how to avoid these mistakes. D4 Solutions uses advanced automation to streamline every stage of production. We use CASS and NCOA for data hygiene purposes, ensuring that your regulated mailings reach the right destination every time. We add Intelligent Mail barcodes to every piece, which allows you to track your envelopes and identify errors, and which also qualifies your shipments for the largest postal discounts you can obtain.

At D4 Solutions, we create audit trails and use automated inserting equipment with camera verification to confirm every document is matched and mailed correctly. Our HIPAA and SOC 2 Type II audited workflows keep sensitive customer data safe for highly regulated industries.

Mail can be difficult to handle in-house without creating undeliverable mail. Partnering with a professional print mail solutions provider such as D4 Solutions lets firms focus on their core operations while ensuring every mailpiece is accurate and efficiently shipped.

Conclusion

Undeliverable mail can drain budgets and hinder both compliance efforts and the customer experience. Common reasons that USPS mail goes undelivered can often be traced back to small data errors and outdated address information, although some USPS mail cannot be delivered to recipients for reasons outside the sender’s control.

If your organization sends time sensitive and highly-regulated documents like statements and legal notifications, you know that undeliverable mail is unacceptable. Regular data cleaning and address validation can prevent the causes of undeliverable mail and improve overall delivery performance.

D4 Solutions understands the importance of accurate and timely mail delivery for highly-regulated industries like finance, healthcare, and government. Our automated processes, use of CASS and NCOA for data hygiene, and robust tracking capabilities help your mail stay compliant and arrive at the right place on time, every time. Reach out to learn about how we can optimize your print and mail workflows.