Gmail 550 5.7.27
Blocked: SPF did not pass
Gmail 550 5.7.27 means: blocked: SPF did not pass. It is a permanent failure, so do not retry it unchanged. Gmail requires bulk senders to pass SPF. Add the sending service to SPF on the envelope domain.
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
This message was blocked because it didn't pass SPF authentication. Gmail requires bulk email senders to authenticate their email with SPF. Authentication results: SPF with ip-address = did not pass To set up SPF for your sending domains, visit Set up SPF. To learn more about Gmail requirements for bulk email senders, visit Email sender guidelines.
| Who sends it | Gmail and Google Workspace |
|---|---|
| Basic code | 550: Requested action not taken: mailbox unavailable (e.g., mailbox not found, no access, or command rejected for policy reasons) (RFC) |
| Enhanced code | 5.7.27: Sender address has null MX |
| Permanent or temporary | Permanent (5xx) |
| Verifying the list prevents it | No |
In practice
The permanent version of the SPF requirement for bulk senders. Gmail moved from rate-limiting to rejecting non-compliant bulk mail during 2024 and 2025. Check SPF for the envelope domain your sending service uses, which may be a subdomain such as bounce.yourdomain.com rather than your main domain.
What the sender should do
Gmail requires bulk senders to pass SPF. Add the sending service to SPF on the envelope domain.
Would verifying the list have prevented Gmail 550 5.7.27?
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 550 5.7.27 mean?
- Gmail 550 5.7.27 means: blocked: SPF did not pass. It is a permanent failure, so do not retry it unchanged. Gmail requires bulk senders to pass SPF. Add the sending service to SPF on the envelope domain.
- Should I retry after Gmail 550 5.7.27?
- No. It is a permanent (5xx) failure, so the same message to the same address will fail again. Fix the cause first. Gmail requires bulk senders to pass SPF. Add the sending service to SPF on the envelope domain.
- Would verifying my list have prevented Gmail 550 5.7.27?
- 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