Mailbox delivery failure policy error

Mailbox delivery failure policy error

Last week, we have got this message from Zoho Mail. I don't understand which policy is fail. Could you give me advise?




This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

   ngoc.tran@tugo.net.vn
    (ultimately generated from  booking@tugo.com.vn )
    SMTP error from remote mail server after RCPT TO:< ngoc.tran@tugo.net.vn >:
    host  mx.zoho.com  [165.254.167.50]: 552 5.1.1 < ngoc.tran@tugo.net.vn > Mailbox delivery failure policy error