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Microsoft Exchange Online outage disrupting worldwide email and calendar access

Service Disruption
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Last updated
Happening score
H score 0
1 unique sources, 1 articles

Summary

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Microsoft Exchange Online mitigated an outage that had blocked customers worldwide from accessing emails and calendars. The disruption also caused email delivery delays and mailbox connection failures, with some users seeing problems in Teams, Outlook, and Hotmail. Microsoft initially tied the problem to a portion of infrastructure in North America, then later said the issue was not region-specific. The outage mattered because it interrupted core communications and required recovery work, including a configuration change, before service returned to normal.

Related Happenings

Microsoft Exchange Online blocks legacy TLS for POP3 and IMAP4 starting July 2026

Security Tool/Service
H score11 First: 28.04.2026 16:18 Last: 28.04.2026 16:18 Sources 1

About this happening: Microsoft will block TLS 1.0 and TLS 1.1 for POP3/IMAP4 access to Exchange Online in July 2026, which could break legacy mail clients and embedded devices...

Open Happening

Microsoft Outlook.com outage causing sign-in failures

Service Disruption
H score20 First: 27.04.2026 15:03 Last: 27.04.2026 15:03 Sources 1

About this happening: Microsoft's Outlook.com is experiencing an ongoing outage that is blocking sign-ins and mailbox access, leaving some customers unable to use email normally. The disruption...

Open Happening

Microsoft Classic Outlook email sending disruption

Service Disruption
H score0 First: 02.04.2026 12:12 Last: 02.04.2026 12:12 Sources 1

About this happening: Microsoft is investigating a Classic Outlook disruption that can prevent some users from sending or replying to email through Outlook.com, causing NDR errors and m...

Latest development: 06.04.2026 22:19

Microsoft fixed a known issue affecting some Classic Outlook users sending emails via Outlook.com that could return non-delivery reports (NDRs) with 0x80070005-0x0004dc-0x000524 errors. Microsoft said the service change was in production as of April 3, 2026, and advised affected users to use the New Outlook client or Outlook.com on the web; Microsoft also pointed users to downloading the Outlook Address Book for affected Outlook.com accounts.

Open Happening

Microsoft classic Outlook Gmail and Yahoo sync disruption

Service Disruption
H score0 First: 24.03.2026 17:12 Last: 24.03.2026 17:12 Sources 1

About this happening: The classic Outlook synchronization failure affecting Gmail and Yahoo accounts has been fixed, restoring email access for impacted users. Microsoft said the bug produc...

Open Happening

Microsoft Exchange Online mailbox access disruption

Service Disruption
H score0 First: 23.03.2026 14:17 Last: 23.03.2026 14:17 Sources 1

About this happening: The Exchange Online service is undergoing an ongoing mailbox access disruption that can stop some users from opening cloud mailboxes through Outlook mobile and the n...

Open Happening

Timeline

  1. 11.09.2025 22:43 2 articles · 10mo ago

    Microsoft Exchange Online outage disrupting worldwide email and calendar access

    Initial Disclosure

    Early on September 11, 2025, users began reporting mailbox access failures and connection problems across Exchange Online. Microsoft initially linked the disruption to a portion of North America infrastructure before later expanding the incident scope and working on mitigation.

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