Help on Code 550

Help on Code 550

Dear Zoho Team,

Please help to solve problem below:

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Ron.Low@msasafety.com, ERROR_CODE :550, ERROR_CODE :permanent failure for one or more recipients ( alva.lim@msasafety.com:blocked,ron.low@msasafety.com:blocked)

Alva.Lim@msasafety.com, ERROR_CODE :550, ERROR_CODE :permanent failure for one or more recipients ( alva.lim@msasafety.com:blocked,ron.low@msasafety.com:blocked)

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 Date:Mon, 23 Jul 2018 17:30:03 +0700
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 To:"Ron MSA" < Ron.Low@msasafety.com>
 Cc:"Alva MSA" < Alva.Lim@msasafety.com>
 Subject:Fw: Portable Gas Detector MSA Altar 5x
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Thanks & Best Regards,
Hung B.M