Exact response pattern
550 5.7.23 Message rejected because of SPF failurePermanentGenericSPF
What it means
The envelope-from domain failed SPF evaluation.
Likely causes
- Sending IP absent from SPF.
- Too many DNS lookups.
- Broken include chain.
- Wrong envelope domain.
Recommended response
- Inspect the actual Return-Path.
- Authorize the sending IP or provider.
- Reduce lookup count and avoid multiple SPF records.
Operational rule: Preserve the complete SMTP response, remote hostname, sending IP, envelope sender and timestamp. Never diagnose from the three-digit code alone.