How to change Default Settings MAILTO app to Outlook APP

Question

Hello,
I want to set view as mailto default application on multiple machines. Is there a way to do this? GPO, Microsoft Configuration Management, etc.

Answer 1

Hello Bakan,

Thank you for posting question on Microsoft Windows Forum.

Based on your query of changing Default Settings MAILTO app to Outlook APP. Well! You can centrally set Outlook as the default MAILTO handler in Windows 11 24H2 using either Group Policy or Microsoft Intune/Configuration Manager with a Default App Associations XML.

For Windows 11 24H2, Microsoft-supported method to enforce default application associations (like MAILTO) is using a Default Associations Configuration File (XML). Direct registry edits, however, (e.g., changing UserChoice keys) no longer work because Windows 11 protects these keys with a unique hash to prevent "app hijacking.".

The suggested deployment methods as following:

• Using Group Policy with a Default Associations XML for Domain-joined machines.
• Using the ApplicationDefaults (DefaultAssociationsConfiguration) CSP (Settings Catalog or custom policy) for Azure AD / Intune-managed devices.

The following are useful articles for your further reference regarding your concerns.

• https://techcommunity.microsoft.com/blog/outlookglobalcustomerservice/set-outlook-as-default-mailto-application/1454942
• https://learn.microsoft.com/en-us/troubleshoot/microsoft-365/admin/group-policy/configure-email-client-using-policy
• https://learn.microsoft.com/en-us/windows/client-management/mdm/policy-csp-applicationdefaults

Hope the above information is helpful! If it is. Free feel to hit "Accepted" for benefitting others in community having the same query too.

Answer 2

To set Outlook as the default application for handling MAILTO links on multiple machines using Group Policy, you can follow these steps:

1. Create an App Associations XML File:
   • On a Windows machine, go to Settings > Default apps.
   • Choose Choose default apps by protocol.
   • Set Outlook as the default app for the MAILTO protocol.
   • Use the DISM tool to export these settings to an XML file. Run the following command in an elevated command prompt:

          Dism /Online /Export-DefaultAppAssociations:"F:\AppAssociations.xml"
     

   • Make a note of the file name and location.
2. Deploy the App Associations XML File via Group Policy:
   • Open the Local Group Policy Editor by typing gpedit.msc.
   • Navigate to Computer Configuration > Administrative Templates > Windows Components > File Explorer.
   • Double-click on Set a default associations configuration file policy and set it to Enabled.
   • Specify the path to the XML file you created earlier (this can be a local path or a network location accessible to all clients).
3. Registry Key Creation:
   • This policy will create a registry key at HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\System with the string value DefaultAssociationsConfiguration pointing to your XML file.
4. Apply the Policy:
   • After setting the policy, the default application associations will be applied the next time users sign in, allowing MAILTO links to open in Outlook.

This method works for domain-joined clients and ensures that Outlook is consistently set as the default email application across multiple machines.

---

References:

• Cannot configure the default email client using Group Policy
• Step 2. Configure Microsoft Outlook
• Start new users in new Outlook
• Launch the default Windows app for a URI