Twilio outage on 2026-08-15: Elevated Microsoft 365 IP Blocks Causing Delivery Failures for Multiple Users

The incident is resolved as block rates at Microsoft 365 have returned to normal levels. Users that continue to see elevated blocks at Microsoft 365 can submit delisting requests to Microsoft by sending an email with a copy of the error message, and the blocked IP address, to "[email protected]". Delisting requests can also be made via the Office 365 Anti-Spam IP Delist Portal at https://sender.office.com/ Users that are experiencing blocks at Microsoft Outlook Consumer domains can open a remediation request at http://olcsupport.office.com/