Facing error 501 in the smartemail inbound log

set user to Email Agent
11/12/2023 17:27:47 9500( 54063) SMIS [INFO][SmartEmailProcessor]: set user to Email Agent
11/12/2023 17:27:48 9500( 54063) SMIS [ERROR][SmartEmailProcessor]: Failed to process it, error code is: 501
11/12/2023 17:27:48 9500( 54063) SMIS [ERROR][Can not move the mail. Exception: ]: Error in MailReceiver.moveMessage. exception:Error calling method: moveMessage Exception (javax.mail.MessagingException: No message find.)