Generic SMTP
451 4.7.0 Temperror — a temporary DNS lookup failure during authentication
451 4.7.0 (Temperror)
Unlike a PermError (a structural problem with the record itself), a Temperror means the DNS lookup needed to evaluate SPF or DKIM failed transiently — a DNS server timeout, an unreachable nameserver, or a lookup that took too long. RFC 7208 requires SPF evaluation to treat this as a temporary failure, which most receivers respond to with a 4xx deferral rather than a hard rejection.
How to fix it
- 1
Check your DNS provider's status
A Temperror on your own domain's records usually means your DNS host had a transient issue. Check their status page.
- 2
Check every include's DNS health
If the error is in a third-party include (an ESP's SPF domain), the problem may be on their DNS, not yours — nothing to fix on your end, it should clear on retry.
- 3
Reduce lookup complexity
A record close to the 10-lookup limit is more exposed to any single slow lookup causing a timeout. Use the SPF checker to see your count, and the SPF flattener if you're near the limit.
- 4
Just wait and retry if it's isolated
A one-off Temperror on otherwise-healthy DNS is usually resolved by the automatic retry built into SMTP — no action needed if it doesn't recur.
Meaning current as of 2026-07-14, cross-checked against the provider's own documentation. Providers do occasionally redefine codes — if this doesn't match what you're seeing, the source link is the authoritative reference.