Yahoo TSS09
Yahoo permanent deferral of your IP
TSS09 is a Yahoo rejection that senders report as a permanent deferral of all mail from their IP, with a note that retrying will not succeed. Unlike TSS04 it does not clear by waiting. Stop sending to Yahoo from that IP, fix the cause, and contact Yahoo through its sender support form.
Should you remove the address?
Keep the address; fix the sending side
Keep the addresses but don't send to them from that IP. The block is on your sending.
Block. Retrying changes nothing until the cause on your side is fixed.
What causes it
- Serious or repeated abuse signals from the sending IP.
- Policy violations Yahoo will not accept.
- The IP is listed by Spamhaus, which Yahoo names as a cause of permanent errors.
How to fix it
In order — try the first one first.
- Stop sending to Yahoo and AOL addresses from the affected IP.
- Check the IP against Spamhaus, which Yahoo names as a cause of permanent errors.
- Find what changed: a new list, a volume spike, a compromised account.
- Submit a Sender Support Request to Yahoo with the full error once the cause is fixed.
Who sends it
Yahoo Mail and AOL.
Yahoo
Yahoo documents 5xx errors as permanent and says not to retry them, listing causes such as policy violations, suspicious behaviour and an IP listed by Spamhaus. It does not list TSS09 by name.
Common questions
- What does SMTP Yahoo TSS09 mean?
- TSS09 is a Yahoo rejection that senders report as a permanent deferral of all mail from their IP, with a note that retrying will not succeed. Unlike TSS04 it does not clear by waiting. Stop sending to Yahoo from that IP, fix the cause, and contact Yahoo through its sender support form.
- Should I retry a Yahoo TSS09 error?
- No. 5xx is a permanent failure, so the message will never be delivered no matter how many times you try. Remove the address — repeated sends to permanent failures are one of the main signals mailbox providers use to throttle a sender.
- How do I fix SMTP Yahoo TSS09?
- Stop sending to Yahoo and AOL addresses from the affected IP.
- Is Yahoo TSS09 a hard bounce or a soft bounce?
- Yahoo TSS09 is a block rather than a classic hard or soft bounce. The rejection is about your sending (authentication, reputation, content or the recipient's policy), not about whether the address exists. Retrying changes nothing until the cause on your side is fixed.
- Should I remove the address after a Yahoo TSS09 bounce?
- Keep the addresses but don't send to them from that IP. The block is on your sending.
- Will verifying my list prevent Yahoo TSS09?
- Not directly. This code is about your authentication, IP or domain reputation, so verification will not lift it. A clean list still matters, because mailbox providers weigh how often a sender hits addresses that don't exist.
Clean the list before the next send.
A bounce report only tells you about the addresses you already mailed. The rest of the list has the same kinds of dead mailboxes in it, and each one becomes a hard bounce recorded against your domain the moment you send.
- A real SMTP mailbox check on every row, before anything is sent
- Dead and mistyped addresses split out, so they never reach your sending tool
- Catch-all, disposable and role addresses flagged alongside
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Sources
Provider wording is quoted only where the provider publishes it.
Last reviewed 2026-10-22