Hi @Microsoft Q & A ,
It is recommended that you refer to this article: use-the-delist-portal-to-remove-yourself-from-the-office-365-blocked-senders-lis
Generally, when an IP was detected to send bulk emails or lots of spam from the IP, this IP was banned by office 365, which prevents all further communication between the IP address and any of our customers through our datacenters.
The most simple way to resolve this issue is using the Office 365 delist portal to remove yourself from the block list.
Please Note: It may take up to 24 hours or results can vary widely before restrictions are removed.
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