How to fix Outlook (OLD) from replacing all Standard app settings after each reboot. Force to use New Outlook.

Nikolaj Sebastian Møller 0 Reputation points
2026-10-08T11:25:37.8+00:00

Hi

However I have to change all standardapps, ie. what program uses MAILTO: protocol. The issue is fixed when i change it manually, however all setting are reverted to old Outlook settings after reboot.

Winver: 25H2 win11
Outlook Old is not in Shell:startup or Taskmgr startup apps.

2026-10-01 13_45_35-Indstillinger

Outlook | Windows | Classic Outlook for Windows | For business
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  1. Aetherin 2,910 Reputation points Independent Advisor
    2026-10-08T12:11:17.67+00:00

    Hi @Nikolaj Sebastian Møller,

    To better understand the issue, could you please provide a few additional details?

    • Is this a personal device, or is it a company-managed device that is connected to a domain, enrolled in Intune, or managed through another device management solution?
    • After restarting Windows, does this issue affect only MAILTO, or are other Outlook-related file types and protocols (.eml, .ics, .msg, ...) also reset to Classic Outlook?
    • Are you an end user or an administrator of your organization?

    Whenever you have a moment, please feel free to reply with the details above by leaving a comment under this post. Your answers will help me better understand your environment and see whether I can identify a suitable direction for further troubleshooting.

    Thank you for your time, and I look forward to your update.

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