Microsoft Outlook is down for the count in a major outage affecting millions of users worldwide for the past 11 hours.

The troubles, according to Microsoft's [1]service status page , began at 2220 UTC on July 9 when it confirmed "users may be unable to access their mailbox using any connection methods."

Microsoft's many Outlooks are confusing users – including its own employees [2]READ MORE

This included Outlook.com, Outlook Mobile, and the Outlook desktop client.

"We've determined that a portion of mailbox infrastructure isn't performing as efficiently as expected, resulting in impact. We're investigating this further to better understand the issue and help inform our next troubleshooting steps," Microsoft stated.

In an update at 0330 UTC on July 10, Microsoft said it was continuing to probe the "impacted mailbox infrastructure" and suspected the glitch was related to an authentication component. In a further update two hours later, it was "further assessing the impact scenario to help inform our next steps to resolve impact."

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In yet one more confession, Microsoft said: "We've determined the cause of the issue and have started deployment of a fix. We expect the fix to take an extended period following our safe change management process."

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At almost 0700 UTC, it perhaps optimistically added: "Our deployment of the fix is progressing quicker than anticipated and we expect impact to gradually mitigate as it progresses. We believe the issue will be resolved by our next update time."

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The next update was scheduled for 1030 UTC today, and if engineers haven't managed to rectify the digital downtime for Outlook then it will have been a full half-day since things went awry.

The [10]last outage for Outlook came in June when we quipped that Microsoft is so keen for users to migrate to the [11]New Outlook email client that it appeared to have broken Classic Outlook… again. On that occasion, the reported issues emerged on virtual desktop infrastructure.

However, the outage last month pales in comparison to the [12]eight-day blackout in early March when Outlook.com users on iOS couldn't access their messages via Apple Mail. Later in the same month, another [13]dubious update broke Outlook once more . ®

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[1] https://portal.office.com/servicestatus/

[2] https://www.theregister.com/2025/03/25/too_many_outlooks/

[3] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/applications&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=2&c=2aG_jlosJymEIiDBgnz4MdQAAAgw&t=ct%3Dns%26unitnum%3D2%26raptor%3Dcondor%26pos%3Dtop%26test%3D0

[4] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/applications&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44aG_jlosJymEIiDBgnz4MdQAAAgw&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0

[5] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/applications&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=3&c=33aG_jlosJymEIiDBgnz4MdQAAAgw&t=ct%3Dns%26unitnum%3D3%26raptor%3Deagle%26pos%3Dmid%26test%3D0

[6] https://www.theregister.com/2025/04/30/microsoft_meta_autocoding/

[7] https://www.theregister.com/2025/04/16/classic_outlook_cpu_spike/

[8] https://www.theregister.com/2025/04/01/google_e2ee_gmail/

[9] https://www.theregister.com/2025/06/26/cost_of_microsoft_dependency/

[10] https://www.theregister.com/2025/06/17/classic_outlook_crash/

[11] https://www.theregister.com/2025/01/30/outlook_arrives_on_windows_10/

[12] https://www.theregister.com/2025/03/11/outlook_ios_problems/

[13] https://www.theregister.com/2025/03/20/outlook_outage_again/

[14] https://whitepapers.theregister.com/