How to modify default mail client in Windows 10
1. Open the Control Panel:
2. In the Control Panel dialog box, in the Search Control Panel textbox, enter Default and choose Default Programs:
3. On the next screen, click Associate a File Type or Protocol with a program link:
4. On the Settings screen, on the right side, click the application under Email group (Mail in this example):
5. Choose the client you prefer:
6. Be sure that selected application is shown instead of the previous one under Email group:
7. Close windows.