Stop receiving from one doamin

Hello,

Two days ago, I complained a vendor that he could not send e-mail to me, before I received messages from him without any problem this problem occur suddenly.

please check the Logs and NDR to advise me to solve this issue:

                            Log

---------51 4.7.0 Timeout waiting for client input

                          NDR

        Could not deliver message to the following recipient(s):

Failed Recipient: x@domain.com
Reason: Remote host said: 601 Attempted to send the message to the following
ip's:
        xx.xx.163.102

thanks