550 5.1.1 — Unknown recipient
Field: SMTPPriority: Medium
What does this error mean?
The server has no name on the recipient’s address.
Probable causes
- No impact
- Removed box
- Alias not available
- Domain not configured
Verification and resolution
- Check the address
- Test the existence of the domain and MX
- Contact the recipient by another means
Precaution: Avoid automatic repeated shipments to an invalid address.
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