SMTP 550 5.1.1 — Recipient address rejected
Domain: EmailPriority: High
What does this error mean?
The recipient address does not exist or is not recognized by the remote mail domain.
Likely causes
- The recipient address is misspelled
- The mailbox was removed
- The expected alias is missing
Checks and resolution
- Verify the recipient address.
- Check the directory or mailbox configuration.
- Verify the domain MX records and retry with a known valid recipient.
Precaution: Avoid repeatedly retrying delivery to an address confirmed as invalid.
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Quick diagnostic.
To diagnose SMTP 550 5.1.1 in the Email domain, start with the following check: Check address. Then check the result against this probable cause: incorrect address. Save context and time of appearance to compare behavior before and after correction. Priority level indicated: High.