Microsoft is currently investigating a widespread service incident affecting Exchange Online mail delivery for customers in North America and Germany. The outage causes significant delays and failures for users attempting to send or receive emails, with some messages remaining undelivered for over an hour. This disruption has been classified as a critical incident due to the high level of impact on business communications.

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Microsoft has addressed a persistent issue that caused the May 2026 security update, KB5089549, to fail on various Windows 11 devices. The problem specifically affected systems where the EFI System Partition (ESP) had 10 MB or less of available free space. During the installation process, affected machines would typically encounter a failure and trigger an automatic rollback during the reboot phase at approximately 35% completion.

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Microsoft has resolved a service disruption that prevented users from configuring multi-factor authentication or accessing the My Sign-Ins portal. The incident was tracked in the Microsoft 365 admin center under the identifier MO1329260. Affected users encountered 504 Gateway Timeout errors when attempting to manage their security credentials or sign-in preferences.

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