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Twilio · Apps and SaaSAug 15, 2026, 01:31 UTC

Widespread Microsoft 365 IP Block Causing Delivery Failures for Multiple Users

InformationalNot disclosedUpdated 20h ago
Aug 15, 01:31 UTCAug 15, 02:05 UTC
Duration
34m
Impact
Informational
Root cause
Not disclosed
Twilio, 90 days
545 incidents
Affected
Not listed by the vendor.
Status page

Final update

The incident is resolved and block rates are back to normal but customers will see change in block classifications from Microsoft 365. Users that continue to see elevated blocks can submit delisting requests to Microsoft by sending an email with a copy of the error message, and the blocked IP address, to "delist@microsoft.com". Delisting requests can also be made via the Office 365 Anti-Spam IP Delist Portal at https://sender.office.com/

Timeline

  1. Resolved · Aug 15, 02:05 UTC
    The incident is resolved and block rates are back to normal but customers will see change in block classifications from Microsoft 365. Users that continue to see elevated blocks can submit delisting requests to Microsoft by sending an email with a copy of the error message, and the blocked IP address, to "delist@microsoft.com". Delisting requests can also be made via the Office 365 Anti-Spam IP Delist Portal at https://sender.office.com/

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Full history

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