Delivery failure

NOTICE: Delivery Failure.

This Delivery Status Notification is sent from MTA...

Your delivery to the following address has been failed.
Please refer to the below for details.
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Delivery failed: info@kfri.re.kr
211.57.34.175 does not like recipient.
Remote host said[Response Message]: 550 5.1.1 Mailbox unavailable info@kfri.re.kr
Giving up on 211.57.34.175.
STEP: RCPT TO