Exact response pattern
550 5.1.4 Destination mailbox address ambiguousPermanentGenericRecipient
What it means
The address maps ambiguously in the destination directory.
Likely causes
- Duplicate aliases or directory objects.
Recommended response
- Recipient administrator must correct directory ambiguity.
Operational rule: Preserve the complete SMTP response, remote hostname, sending IP, envelope sender and timestamp. Never diagnose from the three-digit code alone.