Unable to access Microsoft 365 account – Outlook not connecting on any device

Pablo J Martín R 0 Reputation points
2026-11-12T21:22:37.39+00:00

Hello,

I am experiencing a serious issue accessing my Microsoft 365 Business Standard email account.

Outlook Classic is no longer connecting or synchronizing my emails on my Windows computer. Initially, everything was working correctly on my mobile phone, but now Outlook has also stopped working there.

I have also tried accessing my email through Outlook on the web, but I cannot sign in successfully.

I have verified that my Microsoft 365 subscription is active, my payments are up to date, and my internet connection is working correctly. I have restarted my computer and attempted several troubleshooting steps without success.

I am also experiencing difficulties connecting other email accounts, including Gmail, through Outlook Classic.

I cannot identify the cause of the problem, as everything appears to be correctly configured.

Could you please help me determine why my Microsoft 365 account is not connecting or authenticating across multiple devices, and how to restore access without losing my emails or data?

Thank you for your assistance.

Outlook | Windows | Classic Outlook for Windows | For business

2 answers

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  1. Hendrix 2,775 Reputation points Independent Advisor
    2026-11-12T21:30:26.5366667+00:00

    Hi Pablo,

    Thank you for reaching out.

    Based on my research, Microsoft has officially posted an active service degradation advisory in the Microsoft 365 admin center regarding this outage (tracked under incident ID MO1550821). They are currently investigating a widespread service degradation preventing users from connecting to multiple Microsoft 365 services, including Exchange Online and Outlook on the web.

    User's image

    Currently, Microsoft is actively investigating the issue on their end, so there is no action needed from end users at this time.

    In the meantime, please ask your IT administrator to monitor MO1550821 under Health > Service health for further updates. Having them use the "Report a problem" feature will also help Microsoft log the impact on your organization's tenant.

    You can also follow official updates via MSFT365Status on X

    In case you do not know who your IT admin is, kindly refer to this article: How do I find my Microsoft 365 admin? - Microsoft Support  

    I hope the information I shared earlier was somewhat helpful in addressing your issue. Hope they deploy a fix soon.

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  2. AI answer

    2026-11-12T21:22:57.58+00:00

    If Outlook, mobile, and Outlook on the web all stopped working for the same Microsoft 365 mailbox, the most likely causes in the provided guidance are either a Microsoft 365 service issue or an Outlook profile/AutoDiscover problem on Windows.

    Use this order:

    1. If this affects more than one user in the organization, check Microsoft 365 service health for Exchange Online.
      • This is an admin-only check.
      • A service incident can block access across desktop, mobile, and web at the same time.
    2. On the Windows PC, run the Support and Recovery Assistant for Microsoft 365.
      • It can diagnose and fix several common Outlook connectivity issues automatically.
    3. Make sure Windows and Outlook are fully updated.
      • Out-of-date Outlook or Windows can prevent sending and receiving mail.
    4. Re-create the Outlook profile on Windows.
      • Exit Outlook.
      • Open Control Panel.
      • Search for Mail and open Mail.
      • Select Show Profiles.
      • Select Add.
      • Enter a new profile name and select OK.
      • Complete the Add Account wizard.
      • Back in Mail, select Always use this profile and choose the new profile.
      • Select OK.
      This creates a clean local profile. The guidance indicates this is one of the main fixes for Outlook connection problems and does not remove mailbox data stored in Microsoft 365.
    5. If the issue started after a mailbox migration to Microsoft 365, clear the cached AutoDiscover endpoint.
      • Cause described in the guidance: the pre-migration AutoDiscover server name can remain cached in the Outlook profile in the registry.
      • Set this registry value:
        • HKEY_CURRENT_USER\Software\Microsoft\Office\<x.0>\Outlook\Autodiscover
        • DWORD: ExcludeLastKnownGoodUrl
        • Value: 1
      • Or use:
        • HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\<x.0>\Outlook\Autodiscover
        • DWORD: ExcludeLastKnownGoodUrl
        • Value: 1
      • <x.0> is 16.0 for Office 2016, Microsoft 365, and Office 2019, or 15.0 for Office 2013.
      Warning: registry changes can affect Outlook behavior if entered incorrectly. Prefer creating a new Outlook profile first if registry editing is not appropriate.
    6. If modern authentication was recently enabled and Outlook shows Disconnected, re-create the Outlook profile.
      • This is the documented most effective resolution for that scenario.

    What this means for the current symptoms:

    • Because sign-in is failing in Outlook on the web as well as desktop and mobile, checking service health is the first priority.
    • Rebuilding the Outlook profile helps the Windows client, but it will not fix a tenant-side service outage.
    • If the mailbox was recently migrated, the AutoDiscover registry fix is directly relevant.

    If access still fails after these steps, use the business support path listed in the troubleshooting guidance.

    AI-generated content may be incorrect. Read our transparency notes for more information.

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