Yahoo 553
Permanent failure
Yahoo 553 means: permanent failure. It is a permanent failure, so do not retry it unchanged. Do not retry. If the address is invalid or has forbidden characters, remove it. If the reason is authentication or policy, fix that before the next send to Yahoo.
Yahoo’s exact wording
Quoted from Yahoo Sender Hub: SMTP Error Codes, checked 2026-11-05. Placeholders are Yahoo’s own.
Provider's description
You should not retry sending an email that comes back with with a 5xx error. List managers should have a policy for removing email addresses that generate 5xx errors/bounces.
Provider's description
An email address contains exotic or forbidden characters (e.g. ,$%?{}<>)
Possible cause
You're trying to send a message to an invalid email address.
Possible cause
Your message failed authentication checks against your sending domain's DMARC or DKIM policy.
Possible cause
The message contains characteristics that Yahoo won't accept for policy reasons.
Possible cause
Other suspicious behavior which leads Yahoo to issue a permanent rejection for your SMTP connection.
Possible cause
Your IP is listed by Spamhaus.
| Who sends it | Yahoo and AOL |
|---|---|
| Basic code | 553: Requested action not taken: mailbox name not allowed (e.g., mailbox syntax incorrect) (RFC) |
| Enhanced code | None given |
| Permanent or temporary | Permanent (5xx) |
| Verifying the list prevents it | Partly |
What the sender should do
Do not retry. If the address is invalid or has forbidden characters, remove it. If the reason is authentication or policy, fix that before the next send to Yahoo.
Would verifying the list have prevented Yahoo 553?
Partly
The reply is not only about one address, but providers weigh how often a sender hits addresses that do not exist. Removing bad addresses before sending lowers that signal.
Common questions
- What does Yahoo 553 mean?
- Yahoo 553 means: permanent failure. It is a permanent failure, so do not retry it unchanged. Do not retry. If the address is invalid or has forbidden characters, remove it. If the reason is authentication or policy, fix that before the next send to Yahoo.
- Should I retry after Yahoo 553?
- No. It is a permanent (5xx) failure, so the same message to the same address will fail again. Fix the cause first. Do not retry. If the address is invalid or has forbidden characters, remove it. If the reason is authentication or policy, fix that before the next send to Yahoo.
- Would verifying my list have prevented Yahoo 553?
- Partly. The reply is not only about one address, but providers weigh how often a sender hits addresses that do not exist. Removing bad addresses before sending lowers that signal.
Sources
- Yahoo Sender Hub: SMTP Error Codes (checked 2026-11-05)
- RFC 5321: Simple Mail Transfer Protocol, section 4.2.3 (reply codes) (checked 2026-11-05)
Registry and provider wording is quoted exactly; guidance is written by the SimpleVerifier Team.
SimpleVerifier Team · Last checked against the sources 2026-11-05