Enhanced Status Code 5.7.24: SPF Validation Error
Enhanced Status Code 5.7.24 means “SPF Validation Error.” SPF evaluation could not be completed. This is not a fail, it is a broken record or a DNS problem that stopped the check from producing an answer at all, and many receivers treat that as a fail.
550 5.7.24 SPF record for the sending domain contains suspicious entriesWhat does 5.7.24 mean?
Enhanced status code 5.7.24 means an SPF validation error, which RFC 7372 distinguishes carefully from an SPF fail. A fail means the check completed and the answer was no. An error means the check could not complete: the record is syntactically invalid, it exceeds the permitted DNS lookups, it triggers a void lookup limit, or the DNS query itself failed.
The practical difference matters because the fixes are different. A fail is corrected by adding the sending IP address. An error is corrected by repairing the record itself, and the most common repair is reducing DNS lookups. SPF permits ten, and every include, a, mx, ptr, exists and redirect term counts, including lookups performed inside a provider's own record. A record that has accumulated one include per vendor will cross that line eventually, and it can cross it without you making any change at all, because a vendor expanded their record inside your include.
Google also returns 5.7.24 with text saying the SPF record contains suspicious entries, which covers records using deprecated or dangerous mechanisms such as ptr, records with overly broad address ranges, or records whose includes resolve to something unexpected. In every case the message is the same: the receiver could not arrive at a trustworthy answer, so it declined to guess.
How 5.7.24 plays out
5.7.24 rejectionWhere 5.7.24 sits: soft vs hard bounce
| Soft bounce (4xx) | Hard bounce (5xx) | |
|---|---|---|
| Nature | Temporary | Permanent |
| SMTP class | 4xx | 5xx |
| What to do | Let it retry | Suppress the address |
| Recoverable? | Often | No |
| 5.7.24 is | ✓ this code |
What each provider means by 5.7.24
A registered code does not oblige a provider to use it that way, and the large ones diverge. Match the wording in your own bounce, not the definition above.
Common causes of 5.7.24
- The SPF record exceeds the ten DNS lookup limit and evaluation returns permerror
- The record contains a syntax error such as a stray character or a missing colon
- More than one SPF TXT record is published for the domain, which is invalid
- The record uses the deprecated ptr mechanism, which many receivers reject outright
- An include points at a domain that no longer publishes an SPF record, producing a void lookup
- Authoritative DNS for the domain timed out or answered inconsistently
How to fix 5.7.24
- Count the DNS lookups in the record with SPF Record Checker and get below ten
- Publish exactly one SPF record, merging any duplicates into it
- Remove the ptr mechanism entirely, it is deprecated and actively harmful
- Remove includes for vendors you no longer use, since each one costs a lookup
- Flatten stable includes to ip4 and ip6 ranges where the vendor addresses rarely change
- Check that every include still resolves, since a dead include produces a void lookup