Address Verification - FAQs
What is address verification?
Address verification checks each recipient's address against postal databases to confirm it can receive mail. It runs automatically when you upload a CSV and flags any addresses that cannot be confirmed as deliverable via the Invalid Address filter on your mailing list.
Why was my address marked as invalid?
Common causes include typos, missing suite/unit numbers, non-existent street numbers, PO box formatting errors, or addresses in newly built developments not yet in the postal database.
How do I fix an invalid address?
Open your mailing list, use the Invalid Address filter to find flagged recipients, then click to edit each recipient and correct the address. Once saved, verification runs again automatically.
Is address verification automatic?
Yes - Auto Address Verification runs every time you upload a CSV or add recipients.
Why was the address on my delivered card different from what I entered?
thanks.io uses a CASS-Certified Address Verification system that automatically standardizes and cleanses U.S. addresses to optimize deliverability. International addresses are standardized to uppercase.
After verification, postcards and letters are also run through NCOA (National Change of Address) as required by USPS. NCOA is a USPS database of change-of-address records, and running through it may result in the final printed address being different from what you originally entered. This process reduces undeliverable mail and ensures your pieces reach the right people.
My recipient address is blocked or showing as wrong - what do I do?
If an address is being blocked, it may be a "No Stat" address - a property labeled as inactive (vacant) by the USPS. thanks.io blocks No Stat addresses by default since mail to these addresses is almost certain to be undeliverable.
To turn off No Stat blocking: Go to Account Settings → Mail Preferences → Flag Vacant Addresses and disable the "Check for Vacant Addresses on Orders" toggle. Only disable this if you are intentionally mailing to areas with high new construction, where addresses may exist before the USPS database has been updated.
If you believe a specific blocked address is actually valid and active, you can also request the USPS update its status. Visit postalpro.usps.com/ppro-tools/address-management-system, enter the 5-digit ZIP code, and click "locate" to find the relevant AMS office to contact.