Yahoo 451
Temporary failure (DNS, authentication or deprioritisation)
Yahoo 451 means: temporary failure (DNS, authentication or deprioritisation). It is a temporary failure, so your server retries it. Check that the domains in your MAIL FROM and From header resolve, including an SOA record for any subdomain, and that your name servers answer reliably. Then let the queue retry.
Yahoo’s exact wording
Quoted from Yahoo Sender Hub: SMTP Error Codes, checked 2026-11-05. Placeholders are Yahoo’s own.
Provider's description
These errors indicate that the domain used to the right of the @ in the MAIL FROM or HEADER FROM does not appear to be valid.
Provider's description
We determine if the domain name exists by using an SOA query; therefore, if multiple subdomains are used in MAIL FROM or HEADER FROM commands, then besides setting up a DNS A or MX record (perhaps using a wildcard), then SOA records must be set up as well.
Provider's description
These errors can be returned as either a timeout/servfail (451) or a permfail (554)
Provider's description
If you encounter 4XX errors when trying to send an email to Yahoo, you may retry sending at a later time.
Possible cause
We've observed unusual traffic patterns from your sending server's IP address.
Possible cause
The message you attempted to send included characteristics of spam.
Possible cause
Emails from your mail server have been generating complaints from Yahoo users.
Possible cause
The Yahoo mail servers are busy when attempting a connection.
Possible cause
Other suspicious behavior which leads Yahoo to enforce a dynamic deprioritization for your sender's server.
Possible cause
Your name server was temporarily unavailable.
Possible cause
Authentication results for your domain could not be determined due to a temporary error.
| Who sends it | Yahoo and AOL |
|---|---|
| Basic code | 451: Requested action aborted: local error in processing (RFC) |
| Enhanced code | None given |
| Permanent or temporary | Temporary (4xx) |
| Verifying the list prevents it | No |
What the sender should do
Check that the domains in your MAIL FROM and From header resolve, including an SOA record for any subdomain, and that your name servers answer reliably. Then let the queue retry.
Would verifying the list have prevented Yahoo 451?
No
This reply is about your sending setup, the message or the receiving system, not about whether the address exists, so verifying the list will not prevent it.
Common questions
- What does Yahoo 451 mean?
- Yahoo 451 means: temporary failure (DNS, authentication or deprioritisation). It is a temporary failure, so your server retries it. Check that the domains in your MAIL FROM and From header resolve, including an SOA record for any subdomain, and that your name servers answer reliably. Then let the queue retry.
- Should I retry after Yahoo 451?
- Your sending server retries it automatically, because it is a temporary (4xx) failure. Investigate only if it keeps coming back over several hours.
- Would verifying my list have prevented Yahoo 451?
- No. This reply is about your sending setup, the message or the receiving system, not about whether the address exists, so verifying the list will not prevent it.
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