The short answer
“Returned to sender” means USPS could not or would not deliver a mailpiece as addressed and sent it back to the return address, normally marked with the reason, such as Insufficient Address, No Such Number, Unclaimed, Refused, or Moved, Left No Address. First-Class Mail, Priority Mail, and Certified Mail that cannot be delivered or forwarded is returned at no additional charge; unendorsed USPS Marketing Mail is generally discarded instead. Fix the cause named on the label, then mail the item again in a new envelope with new postage.
What “return to sender” means
A returned envelope is the Postal Service telling you it could not complete delivery. The Domestic Mail Manual (DMM 507.1.1) lists the underlying causes: no postage, an incomplete, illegible, or incorrect address, an addressee who is not at the address because they are unknown, moved, or deceased, mail that went unclaimed, mail the addressee refused, and items that do not meet mailability rules.
When a piece is undeliverable, USPS marks it with an endorsement that names the reason and routes it back to the return address. That endorsement is the most useful clue you have, so read it before you change anything. Mail without a usable return address cannot simply come back to you; if USPS cannot identify the sender, it becomes dead mail.
Two details from the USPS FAQ explain a lot of confusion. Returned mail travels back in the same mail class it was sent in, and USPS does not notify the sender when an untracked piece is returned. You usually learn about it only when the envelope reappears in your mailbox.
USPS return reasons and how to fix each one
These are the endorsements you are most likely to see, with the definition USPS gives in DMM Exhibit 507.1.4.1 and a practical next step. The exact wording on a returned label can be abbreviated.
| Endorsement | What USPS means | What to do |
|---|---|---|
| Attempted – Not Known | Delivery was attempted, but the addressee is not known at that address. | Confirm that the person or business still uses the address, and ask them for a current one. |
| Insufficient Address | The number, street, box number, route number, or city and state is missing, and the correct address is not known. | Add the missing element, such as the house number, apartment or suite, or PO Box number, and check the ZIP Code. |
| No Such Number | The street number does not exist and the correct number is not known. | Check for transposed digits and look the address up with the USPS ZIP Code tool. |
| No Such Street | The street does not exist in that city, and the correct street is not known. | Check the spelling, the suffix (Street, Avenue, Court), and the city. |
| Moved, Left No Address | The addressee moved and did not file a change-of-address order. | Get the new address directly from the recipient or another reliable record. |
| Not Deliverable as Addressed – Unable to Forward | The mail cannot be delivered as addressed, and no forwarding order is on file or the forwarding order has expired. | Treat the old address as out of date and confirm a current one before resending. |
| Vacant | The house, apartment, office, or building is not occupied. The DMM reserves this endorsement for mail addressed to “Occupant.” | Remove the address from your list unless you have reason to believe it is occupied again. |
| Unclaimed | The addressee did not pick up the item or abandoned it. | Contact the recipient another way; for a signature service, consider whether a different method fits the situation. |
| Refused | The addressee refused to accept the mail or to pay postage due on it. | Do not keep resending; contact the recipient another way if the matter still needs a response. |
| No Mail Receptacle | The addressee has not provided a mailbox or other receptacle. | Ask the recipient for a PO Box or another deliverable address. |
| Returned for Postage | The piece had no postage or the postage fell off. | Remail with full postage in a new envelope. |
What happens to First-Class Mail, Certified Mail, and marketing mail
The mail class decides whether an undeliverable piece is forwarded, returned, or thrown away. Under DMM 507.1.8.3, First-Class Mail, Priority Mail, Priority Mail Express, and USPS Ground Advantage pieces that cannot be delivered or forwarded are returned to the sender at no additional charge, unless the sender asked for different treatment.
For First-Class Mail without a special endorsement, a change-of-address order changes the outcome. During the first 12 months after a move, the piece is forwarded to the new address. In months 13 through 18, it is returned to you with the new address attached, which is why some returned envelopes carry a label showing where the person moved. After 18 months, it is returned with the reason for nondelivery.
Certified Mail that cannot be delivered is treated like First-Class Mail, and a return receipt attached to a returned Certified piece stays on it and comes back to you. USPS Marketing Mail works differently: without a mailer endorsement, undeliverable pieces are disposed of rather than returned. Every Door Direct Mail Retail pieces get no forwarding or return service at all.
How long does it take for mail to be returned?
USPS does not publish a single return time. Its FAQ says the time depends on the services purchased, the mail class, and recipient services such as a change of address or Hold Mail, and it advises against expecting a specific return date.
Signature services add a waiting period. When a Certified Mail, Registered Mail, or similar item cannot be delivered, the carrier leaves a notice. If the item is not picked up and redelivery is not requested, DMM 508.1.1.7 says it is returned after 15 days, or 5 days for Priority Mail Express and 10 days for COD, unless the sender specified fewer days. The trip back to you comes after that holding period.
What to do when USPS says returned to sender
Work from the endorsement rather than guessing. A wrong apartment number and a refused letter need very different responses.
- Read the endorsement or label and note the reason and any new address shown.
- Confirm the address with the recipient or a reliable record, and check the street, number, unit, and ZIP Code with the USPS ZIP Code lookup.
- Update the address wherever you keep it, so the next mailing does not repeat the problem.
- Put the contents in a new envelope with new postage. USPS asks for this because the prominent “Return to Sender” marking can cause a reused envelope to be returned again.
- If the mailing relates to a deadline or required notice, keep the returned envelope as you received it and confirm the acceptable next step with whoever set the requirement.
How to refuse mail and send it back
You can refuse mail without paying anything if you have not opened it. The USPS FAQ says to mark the piece “Refused” and return it unopened within a reasonable time. Once a piece is opened, even if resealed, it can no longer be refused; returning it means a new envelope, a correct address, and new postage.
Signature mail has its own rule. Registered Mail, insured mail, Certified Mail, and COD items cannot be refused after you accept delivery. To refuse one before signing, check the “Refused” box on the back of the delivery notice, sign by the “X,” and put the notice back in your mailbox. For unwanted advertising, USPS points to the independent DMAchoice service to reduce prospect mailing lists.
If you mailed the piece through IRIS
IRIS prints the return address you enter on each letter or postcard, so a returned piece comes back to that address, not to IRIS. Check the return address as carefully as the recipient address before you pay.
When the print partner reports a return, a reroute, or a Certified Mail issue, the order page shows “Delivery exception,” and the specific event tells you which one occurred. Ordinary First-Class pieces can have few or no scans, so a return can reach your mailbox without any order update. A returned order is not mailed again automatically: confirm the corrected address, then place a new order.
Sources & further reading
Product details checked against the IRIS API contract when this article was published. Platform references can change; consult the linked documentation when implementing.
- USPS Domestic Mail Manual 507, Mailer Services (treatment of undeliverable mail)
- USPS Domestic Mail Manual 508, Recipient Services (notice and hold periods)
- USPS FAQ, Return to Sender Mail
- USPS FAQ, Refuse unwanted mail and remove name from mailing lists
Published by IRIS Postal Forms, operated by Great Lakes Computing Office LLC. Send a correction.