Resolved after 16 days 20 hours, affecting Business Email, on December 16, 2025.
We are aware of an increase in email delivery issues affecting messages sent from Microsoft 365/Outlook to Premium Business email-hosted mailboxes. Some emails may bounce or be delayed due to Microsoft IP addresses appearing on the SenderScore blocklist. If you are experiencing this issue, you can resolve it by safelisting Microsoft's sending IP addresses at the mailbox level: 1. Go to cp.rackspace.com > Domains > Spam settings > Safelists 2. Select your domain 3. Add the following IP ranges: 52.102.%.% 40.107.%.% 52.101.%.% 52.103.%.% We are actively working with our partners to determine if fleet-wide mitigations can be applied. We will provide updates as more information becomes available. If you have any questions or concerns, please don't hesitate to contact us via Live Chat or by opening a case.
Affected components
Update timeline
- investigating Dec 16, 2025, 10:16 PM UTC
We are aware of an increase in email delivery issues affecting messages sent from Microsoft 365/Outlook to Premium Business email-hosted mailboxes. Some emails may bounce or be delayed due to Microsoft IP addresses appearing on the SenderScore blocklist. If you are experiencing this issue, you can resolve it by safelisting Microsoft's sending IP addresses at the mailbox level: 1. Go to cp.rackspace.com > Domains > Spam settings > Safelists 2. Select your domain 3. Add the following IP ranges: 52.102.%.% 40.107.%.% 52.101.%.% 52.103.%.% We are actively working with our partners to determine if fleet-wide mitigations can be applied. We will provide updates as more information becomes available. If you have any questions or concerns, please don't hesitate to contact us via Live Chat or by opening a case.
- resolved Jan 02, 2026, 07:02 PM UTC
This incident has been resolved.
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