Microsoft Alert: Service degradation – Exchange Online – Users are receiving an error when attempting to delist blocked IP addresses at https://sender.office.com – RESOLVED

30-07-2021 09:36:07 AM (BST)

Issue Reported: 29/07/2021 5:45:00 PM

Microsoft Reference : EX274026 

Issue Status: RESOLVED

Issue Description: Users are receiving an error when attempting to delist blocked IP addresses at https://sender.office.com.

Users are seeing the following error message when attempting to delist blocked IP addresses:
“5.1.0 – Unknown address error 550-‘5.7.606 Access denied”

Scope of impact: This issue may impact any user attempting to delist blocked IP addresses at https://sender.office.com.

Final Update – 30/07/2021 09:36:00 AM: A recent configuration change designed to migrate system-generated outbound mail was preventing users from delisting blocked IP addresses at https://sender.office.com. Following Microsoft additional internal validation, have confirmed that impact has been resolved.

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