Exact response pattern
550 5.7.54 Unable to relay recipient in non-accepted domainPermanentGenericRelay
What it means
The SMTP server is not configured to relay to the recipient domain for this session.
Likely causes
- Wrong connector.
- Unauthenticated relay attempt.
- Recipient domain not accepted.
Recommended response
- Use the correct authenticated submission service.
- Fix connector or accepted-domain configuration.
- Do not treat this as an IP reputation problem.
Operational rule: Preserve the complete SMTP response, remote hostname, sending IP, envelope sender and timestamp. Never diagnose from the three-digit code alone.