why is our IP is being block by hotmail and how to resolve it?

From this morning, my mail server(IP:133.242.83.178) cannot send/receive from Hotmail.

And the error message is

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550 OU-002

(BAY004-MC5F16) Unfortunately, messages from 103.29.74.115 weren't sent.

Please contact your Internet service provider since part of their network

is on our block list. You can also refer your provider to

FROM command)

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that's not make any sense,because my server IP is even not 103.29.74.115.

Could anybody tell my how can I solve this ploblems?

Sorry for my poor English.

Question about Outlook Express