How do I change the email app that is opened when clicking on an email address?
This is changed through the Windows settings.
Go to Windows Settings | Apps | Default apps. Under Set defaults for applications, search for your email app and click on it. Change the MAILTO app to the app of your choice.
Go to Windows Settings | Apps | Default apps. Change Email to the app of your choice.
For Windows 8 and below
You can find an option to set the default e-mail software under Settings > Control Panel > Internet Options > Programs. If not found, in Explorer, select Options under the View menu, and select the File Types tab. Select URL:MailTo Protocol, double-click open, and enter the mail software path and options on Application used to perform action. Refer to the e-mail program help because the options depend on each mail software. Some e-mail programs do not support this function.