--- title: Microsoft tests fix for latest hours-long Outlook outage description: Microsoft confirmed a widespread, multi-hour outage affecting Exchange Online and Outlook, causing email delays, failures, and authentication errors for... canonical: https://daily.dev/posts/microsoft-tests-fix-for-latest-hours-long-outlook-outage-p9tn5amyy twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Microsoft tests fix for latest hours-long Outlook outage | daily.dev og:description: Microsoft confirmed a widespread, multi-hour outage affecting Exchange Online and Outlook, causing email delays, failures, and authentication errors for... og:url: https://daily.dev/posts/microsoft-tests-fix-for-latest-hours-long-outlook-outage-p9tn5amyy og:image: https://api.daily.dev/og/posts/p9tN5Amyy.png og:image:alt: Microsoft tests fix for latest hours-long Outlook outage og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Microsoft tests fix for latest hours-long Outlook outage **[TechCrunch](https://daily.dev/sources/tc)** · 2 min read · 0 upvotes · 1 comments ## Summary Microsoft confirmed a widespread, multi-hour outage affecting Exchange Online and Outlook, causing email delays, failures, and authentication errors for business users. The company traced the issue to an authentication component and is testing a remediation strategy on a subset of infrastructure before rolling it out broadly. User reports began around 11:30 AM ET Monday, with over 5,000 reports on Downdetector by 2 PM ET. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### What caused the Outlook and Exchange Online outage on Microsoft 365? Microsoft identified the issue as related to an authentication component within Exchange Online, causing degraded functionality across various services. Affected users experienced delays and failures sending or receiving messages, mailbox search failures, authentication errors, and other mailbox operation problems. Microsoft was testing a remediation strategy on a portion of its infrastructure before a broader rollout. _Track infrastructure incidents like this Exchange Online outage as they unfold on daily.dev._ ## Similar posts on daily.dev - [Microsoft Exchange Online outage causes email delays, failures](https://daily.dev/posts/microsoft-exchange-online-outage-causes-email-delays-failures-iugzphfkb) · BleepingComputer · 0 upvotes · 0 comments - [Microsoft says Outlook.com outage is causing sign‑in failures](https://daily.dev/posts/microsoft-says-outlook-com-outage-is-causing-sign-in-failures-a12xjffx3) · BleepingComputer · 2 upvotes · 1 comments - [Microsoft 365 hit by outage, preventing access to emails and files](https://daily.dev/posts/microsoft-365-hit-by-outage-preventing-access-to-emails-and-files-irywo2f8j) · TechCrunch · 0 upvotes · 0 comments - [Microsoft asks iPhone users to reauthenticate after Outlook outage](https://daily.dev/posts/microsoft-asks-iphone-users-to-reauthenticate-after-outlook-outage-oly28bv0c) · BleepingComputer · 0 upvotes · 0 comments - [Microsoft confirms outage affecting search in Microsoft 365 apps](https://daily.dev/posts/microsoft-confirms-outage-affecting-search-in-microsoft-365-apps-kbc6i6lst) · BleepingComputer · 0 upvotes · 0 comments --- Tags: [#microsoft](https://daily.dev/tags/microsoft) [View this post on daily.dev](https://daily.dev/posts/microsoft-tests-fix-for-latest-hours-long-outlook-outage-p9tn5amyy) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Microsoft tests fix for latest hours-long Outlook outage","url":"https://daily.dev/posts/microsoft-tests-fix-for-latest-hours-long-outlook-outage-p9tn5amyy","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/microsoft-tests-fix-for-latest-hours-long-outlook-outage-p9tn5amyy"},"datePublished":"2026-08-31T19:01:11.562Z","dateModified":"2026-08-31T19:23:04.114Z","description":"Microsoft confirmed a widespread, multi-hour outage affecting Exchange Online and Outlook, causing email delays, failures, and authentication errors for...","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/3e2fb181c70d4a9cca7a0748fa3d2c8a?_a=AQAEuop","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/3e2fb181c70d4a9cca7a0748fa3d2c8a?_a=AQAEuop","isAccessibleForFree":true,"articleSection":"TechCrunch","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"TechCrunch","logo":"https://media.daily.dev/image/upload/t_logo,f_auto/v1/logos/tc","url":"https://daily.dev/sources/tc"},"commentCount":1,"discussionUrl":"https://daily.dev/posts/microsoft-tests-fix-for-latest-hours-long-outlook-outage-p9tn5amyy","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":1}],"keywords":"microsoft","timeRequired":"PT2M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"TechCrunch","item":"https://daily.dev/sources/tc"},{"@type":"ListItem","position":3,"name":"Microsoft tests fix for latest hours-long Outlook outage"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/microsoft-tests-fix-for-latest-hours-long-outlook-outage-p9tn5amyy#faq","mainEntity":[{"@type":"Question","name":"What caused the Outlook and Exchange Online outage on Microsoft 365?","acceptedAnswer":{"@type":"Answer","text":"Microsoft identified the issue as related to an authentication component within Exchange Online, causing degraded functionality across various services. 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