Gmail 451 4.7.26
DMARC check hit a temporary DNS failure
Gmail 451 4.7.26 means: dMARC check hit a temporary DNS failure. It is a temporary failure, so your server retries it. Gmail could not complete DMARC because of a temporary DNS failure. Check that your SPF, DKIM and DMARC records resolve reliably; the message should go through on retry.
Gmail’s exact wording
Quoted from Google Workspace Admin Help: Gmail SMTP errors and codes, checked 2026-11-05. Placeholders are Gmail’s own.
Reply text
Unauthenticated email from domain-name is not accepted due to domain's DMARC policy, but temporary DNS failures prevent authentication. Please contact the administrator of domain-name domain if this was a legitimate email. To learn about the DMARC initiative, go to Control unauthenticated mail from your domain.
| Who sends it | Gmail and Google Workspace |
|---|---|
| Basic code | 451: Requested action aborted: local error in processing (RFC) |
| Enhanced code | 4.7.26: Multiple authentication checks failed |
| Permanent or temporary | Temporary (4xx) |
| Verifying the list prevents it | No |
In practice
This code is different from 421 4.7.26. Gmail tried to check DMARC, but a temporary DNS failure stopped it, so it will not accept the message yet. If it happens often, your domain's DNS is unreliable or slow, which also affects SPF and DKIM lookups. Check that your name servers answer from several locations and that records have sensible TTLs.
What the sender should do
Gmail could not complete DMARC because of a temporary DNS failure. Check that your SPF, DKIM and DMARC records resolve reliably; the message should go through on retry.
Would verifying the list have prevented Gmail 451 4.7.26?
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 Gmail 451 4.7.26 mean?
- Gmail 451 4.7.26 means: dMARC check hit a temporary DNS failure. It is a temporary failure, so your server retries it. Gmail could not complete DMARC because of a temporary DNS failure. Check that your SPF, DKIM and DMARC records resolve reliably; the message should go through on retry.
- Should I retry after Gmail 451 4.7.26?
- 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 Gmail 451 4.7.26?
- 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.
The same code elsewhere
Sources
- Google Workspace Admin Help: Gmail SMTP errors and codes (checked 2026-11-05)
- IANA: SMTP Enhanced Status Codes registry (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