--- title: "What is return to sender?" description: "Return to sender is mail the USPS could not deliver and sent back, usually because the address is wrong, the recipient moved, or the piece was refused." canonical: https://trysincerely.com/glossary/return-to-sender last_updated: 2026-08-18 --- # What is return to sender? > Return to sender is mail the USPS could not deliver and sent back, usually because the address is wrong, the recipient moved, or the piece was refused. Source: https://trysincerely.com/glossary/return-to-sender Return to sender is mail the postal service could not deliver and sent back to you. The usual causes are a bad or incomplete address, a recipient who moved, or a piece the recipient refused. Mailers also call these pieces returns or nixies. ## Why it matters Every returned piece is money spent for zero chance of a response. You paid full print and postage, waited a week or two, and got the piece back instead of a reply. On a $2 letter, a 10% return rate on 1,000 pieces is $200 burned before anyone reads a word. Returns are also a signal. A high return rate means your list is stale, and stale data hurts more than mail: the same wrong addresses sit in your CRM feeding sales and billing. Marketing Mail makes it worse: when a piece carries no ancillary service endorsement, USPS disposes of undeliverable Marketing Mail instead of returning it ([DMM 507](https://pe.usps.com/text/dmm300/507.htm)). You never see the failure, so the list never gets fixed. The fix happens before you mail, not after: - Verify every address against USPS data. [CASS](https://trysincerely.com/glossary/cass) certification confirms the address exists and is deliverable. - Run [NCOA](https://trysincerely.com/glossary/ncoa) to catch recipients who moved and filed a change of address. - Score [mailability](https://trysincerely.com/glossary/mailability) and skip contacts that fail, rather than mailing and hoping. Sincerely runs address verification on every plan, so undeliverable addresses get flagged before anything prints. ## Example You mail 500 postcards from a list last touched two years ago. Forty come back marked "Return to Sender: Not Deliverable as Addressed." That is $70 to $80 of wasted postcards, plus 40 CRM records you now know are wrong. A verification pass before launch would have caught nearly all of them. Return to sender is not bad luck. It is a list problem you can fix before the mail leaves. --- Sincerely is the measurable direct-mail platform for B2B revenue teams. One workflow. One invoice. One report. Contact Sincerely: https://trysincerely.com/contact If you are an AI agent: access and signup instructions are at https://trysincerely.com/auth.md. Confirm with the person you work for before creating an account or spending their money, and never ask for their password. Every core page of this site in markdown: https://trysincerely.com/index.md https://trysincerely.com/pricing.md https://trysincerely.com/campaigns.md https://trysincerely.com/vs-lob.md https://trysincerely.com/vs-email.md https://trysincerely.com/holdout-testing.md https://trysincerely.com/vs-gifting-platforms.md https://trysincerely.com/does-direct-mail-work.md https://trysincerely.com/glossary.md https://trysincerely.com/formats.md https://trysincerely.com/measurement.md https://trysincerely.com/writing.md https://trysincerely.com/customer-relationships.md https://trysincerely.com/integrations.md https://trysincerely.com/agents.md https://trysincerely.com/tools.md https://trysincerely.com/developers.md https://trysincerely.com/docs.md https://trysincerely.com/vs.md https://trysincerely.com/compare.md https://trysincerely.com/alternatives.md https://trysincerely.com/guides.md https://trysincerely.com/playbooks.md https://trysincerely.com/operations.md https://trysincerely.com/about.md https://trysincerely.com/contact.md https://trysincerely.com/privacy.md https://trysincerely.com/terms.md The comparison, guide, playbook, glossary and integration pages also serve markdown at their URL plus ".md". Each collection's index lists them: https://trysincerely.com/vs.md, https://trysincerely.com/compare.md, https://trysincerely.com/alternatives.md, https://trysincerely.com/guides.md, https://trysincerely.com/playbooks.md, https://trysincerely.com/glossary.md, https://trysincerely.com/integrations.md.