5.7.24: SPF check error
The receiving server could not complete the SPF check for the sender's domain, either because of a temporary DNS problem or because the SPF record is broken.
- Standard
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 5.7.24
- Provider
- Standard SMTP codes
- Temporary or permanent
- PermanentRefused for good: the message comes back to the sender, and resending it gets the same answer.
- Who has to act
- The sender. The fix is on the sending side: your domain, your server or your list.
- What the server says
5.7.24 SPF validation error
What it means
X.7.24 replaces two older codes from RFC 7208. A temperror (a transient DNS failure during the check) was to be reported as 451 4.4.3, and a permerror (a record that cannot be interpreted) as 550 5.5.2; RFC 7372 registered X.7.24 for both, with reply 451 or 550. So 4.7.24 means the lookup failed for a moment and the sending server will retry, while 5.7.24 means the record itself is invalid and every message will fail until it is fixed. Common permerror causes are two SPF records on one domain, a syntax error, or more than 10 DNS lookups.
Common causes
- Two separate SPF records on the same domain.
- A syntax error in the SPF record, such as a misspelled mechanism.
- More than 10 DNS lookups through include, a, mx and similar mechanisms.
- A temporary outage at the domain's DNS provider (4.7.24).
How to fix it
- 01Look up the domain's SPF record and check it for errors.
- 02Merge multiple SPF records into one.
- 03Reduce the number of include mechanisms, or replace some with ip4:/ip6: ranges.
- 04For 4.7.24, let the queue retry and check that your DNS servers answer.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
- RFC 7372, section 3.2: SPF Failure Codesrfc-editor.org
- RFC 7208, section 8.6: Temperror (SPF)rfc-editor.org
- RFC 7208, section 8.7: Permerror (SPF)rfc-editor.org
- RFC 7208, section 4.6.4: DNS Lookup Limits (SPF)rfc-editor.org
- IANA, SMTP Enhanced Status Codes registry (Enumerated Status Codes)iana.org
Related codes
- 550 5.7.23SPF check failed.The SPF check on the sending server's IP address gave a fail result for the sender's domain, and the receiving server's policy rejects such mail.
- 4.4.3DNS or directory lookup failed.The message could not be passed on because a directory server, most often DNS, did not answer; the lookup and the delivery are retried.
- 5.5.2SMTP syntax error.A command from the sending software could not be understood, because its syntax was wrong or the command was not recognised at all.
5.7.24 at other providers
Further reading
All 105 standard codesEvery code in the wikiPaste your own bounce