After switching from Classic Outlook to the new Outlook for Windows, many users find that mailto links no longer open in Outlook. Instead, web browsers or other email apps intercept these links. This happens because Windows stores the default mail client setting separately from the Outlook app itself. When you install new Outlook, it does not automatically claim the default mail client role from Classic Outlook. This article explains how to set new Outlook as your default mail client in Windows 10 and Windows 11 so mailto links always open in the correct app.
Key Takeaways: Setting New Outlook as the Default Mail Client
- Settings > Apps > Default apps > Set defaults by app: Select new Outlook and click “Set this program as default” to register it for mailto, EML, and MSG file types.
- Control Panel > Default Programs > Set Your Default Programs: An alternative method that works identically in Windows 10 and Windows 11 for changing the default email program.
- New Outlook in-app toggle under Settings > General: Enables or disables Outlook as the default mail handler directly from within the application.
Why New Outlook Does Not Automatically Become the Default Mail Client
When you first launch new Outlook, it runs alongside Classic Outlook without modifying the Windows default app associations. The Windows registry entry for the default mail client remains set to Classic Outlook or a previous email application. This is by design — Microsoft does not want to silently override a user’s existing default app choice.
The default mail client setting controls which program handles mailto links, EML files, and MSG files. If you click a mailto link on a website or in a document, Windows checks the default mail client registry key and opens the associated application. Because new Outlook does not update this key during installation, you must change it manually.
How Windows Stores the Default Mail Client
Windows 10 and Windows 11 store default app associations in the user profile registry hive. The key for email is located under HKEY_CURRENT_USER\Software\Microsoft\Windows\Shell\Associations\UrlAssociations\mailto\UserChoice. Changing the default via the Settings app or Control Panel updates this key. New Outlook registers itself as a candidate for this association but does not claim it automatically.
Steps to Set New Outlook as the Default Mail Client in Windows 11
- Open Windows Settings
Press Windows + I to open Settings. Click Apps in the left sidebar, then click Default apps. - Search for Outlook
In the “Set defaults for applications” search box, type Outlook. The results show both Classic Outlook and new Outlook. - Select new Outlook
Click the Outlook (new) entry. Do not click Classic Outlook. A list of file types and link types appears. - Set mailto default
Locate MAILTO in the list. Click the current default app (likely Classic Outlook or your browser). A popup shows available apps. Select Outlook (new). Click Set default. - Set EML and MSG defaults
Scroll down to .eml and .msg file types. Repeat the same process: click the current default, choose Outlook (new), and confirm. Close Settings when done.
Steps to Set New Outlook as the Default Mail Client in Windows 10
- Open Windows Settings
Click the Start button, then the gear icon to open Settings. Click Apps, then click Default apps. - Change the email default
Under the “Email” section, click the current app icon (for example, Classic Outlook or Mail). A list of installed email apps appears. - Select new Outlook
Click Outlook (new) from the list. Windows immediately updates the default mail client. Close Settings. - Verify the change
Open a web browser and click a mailto link on any page. The link should open a new email compose window in new Outlook.
Using the Control Panel Method for Both Windows 10 and Windows 11
- Open Control Panel
Press Windows + R, type control, and press Enter. Click Programs, then click Default Programs. - Open Set Your Default Programs
Click Set your default programs. Wait for the list of installed programs to load. - Select new Outlook
Scroll down and click Outlook (new). Click Choose defaults for this program. - Select all file and link types
Check the boxes for .eml, .msg, mailto, and any other Outlook-related types. Click Save. Click OK to close.
Setting the Default Directly Inside New Outlook
- Open new Outlook
Launch the new Outlook app. Click the Settings gear icon in the top-right corner. - Go to General settings
Click General in the left sidebar. Scroll down to the Default app section. - Toggle the default setting
Turn on the toggle labeled Make Outlook the default email app. A Windows popup may ask for confirmation. Click Yes. New Outlook now handles mailto links and email files.
If New Outlook Still Does Not Open Mailto Links
Mailto links open in your web browser instead of Outlook
Your browser may have its own setting for handling mailto links. In Google Chrome, go to Settings > Privacy and security > Site Settings > Additional permissions > Protocol handlers. Ensure Outlook is selected. In Microsoft Edge, go to Settings > Cookies and site permissions > Protocol handlers. Set Outlook as the default. If the browser setting overrides Windows, change it there.
Classic Outlook keeps opening when you click a mailto link
This indicates the default app setting still points to Classic Outlook. Repeat the steps in the Settings app and verify you selected Outlook (new) specifically. If both versions appear identical, right-click the Start button, select Apps and Features, locate Classic Outlook, and choose Modify. Run a repair installation. After repair, repeat the default app change.
Windows shows “You’ll need a new app to open this mailto link”
This error means the mailto association is missing or corrupted. Open Settings > Apps > Default apps. Scroll to the bottom and click Reset to the Microsoft recommended defaults. This resets all app associations. Then repeat the steps to set new Outlook as the default for mailto, .eml, and .msg. If the error persists, run the Windows Store Apps troubleshooter from Settings > System > Troubleshoot > Other troubleshooters.
New Outlook vs Classic Outlook as Default Mail Client: Key Differences
| Item | New Outlook (Default) | Classic Outlook (Default) |
|---|---|---|
| Mailto link handling | Opens a new compose window in new Outlook | Opens a new compose window in Classic Outlook |
| EML file association | Opens .eml files in new Outlook | Opens .eml files in Classic Outlook |
| MSG file association | Opens .msg files in new Outlook | Opens .msg files in Classic Outlook |
| In-app default toggle | Available under Settings > General | Not available; uses File > Options > General |
| Windows Settings integration | Appears as “Outlook (new)” | Appears as “Microsoft Outlook” |
After setting new Outlook as the default mail client, test the change by clicking a mailto link on a webpage. If the correct app opens, the configuration is complete. You can also right-click an .eml file in File Explorer and select Open with > Outlook (new) and check the “Always use this app” box for a quicker setup. If you ever need to switch back to Classic Outlook, repeat the same steps and select Classic Outlook instead.