Duplicates & Suppression - FAQs
What is Duplicate Prevention?
Duplicate Prevention prevents the same recipient from receiving more than one piece of mail from your account within a 36-hour window, account-wide across all lists and campaign types.
How does the 36-hour window work?
When mail is sent to a recipient, thanks.io records the send timestamp. If another send is attempted for the same recipient within 36 hours, it is blocked and marked "Duplicate Prevented." The window resets after 36 hours.
Can I disable Duplicate Prevention?
Yes. Go to Account Settings → Mail Preferences and toggle off Enable Dedupe Failsafe under the Duplicate Prevention section. When off, duplicate checks are disabled account-wide. Gift cards are unaffected either way.
Does Duplicate Prevention stop me buying the same mailing list twice?
No. Duplicate Prevention only governs mail sends. Duplicate mailing list purchases are covered by a separate check: an identical Radius Search purchase from your account is refused within 24 hours of the first one, so a double-clicked button or a retried integration does not buy the same records twice. See Duplicate purchase protection.
My Radius Search was refused as a duplicate. What do I do?
Use the purchase you already made. The refusal returns the mailing list ID from the original purchase, and the order ID as well when the search was bought as part of a mail order - find that list under Mailing Lists and send from it instead of buying again. Over the API the refusal is an HTTP 409 with code: duplicate_radius_search; through Zapier it comes back as an HTTP 200 carrying the same fields so the Zap does not retry.
If you genuinely want to buy the same neighborhood again, change any search parameter (a different number of records, a different record type, a different target list) or wait out the 24 hours.
I want to mail the same neighborhood twice. Is that blocked?
No. When a Radius Search is bought as part of a mail order, the order is compared too, so a second mailer with different creative to the same neighborhood goes through. Only the identical send, repeated within 24 hours, is refused.
My Radius Search purchase failed. Can I retry right away?
If nothing was charged - no neighbors were found, the search returned no results, or the order was cancelled inside its review window - the block is released immediately and you can retry straight away. If the purchase failed after your account was charged, the block is kept on purpose so a retry cannot double-buy; contact support to have it cleared.
What is a Suppression List?
A Suppression List contains recipients who should never receive mail from your account. They are permanently skipped on all future sends, regardless of which list or campaign triggers the send.
How is a Suppression List different from Duplicate Prevention?
Duplicate Prevention is a temporary, time-based block (expires after 36 hours). A Suppression List is a permanent exclusion. Use Suppression Lists for opt-outs; Duplicate Prevention handles accidental double-sends. Neither one governs data purchases - that is the 24-hour duplicate Radius Search purchase window.