Although you may have a desktop email client, such as Microsoft Outlook or Mozilla Thunderbird installed on your computer, clicking "Mail to" hyperlinks causes your computer to launch the default Mail app that comes pre-installed with Windows 8.1. You can, however, prevent the Mail app from showing up by setting your preferred email client as the default email application via the operating system itself, or by directly configuring your Web browser.
Change PC Settings
Press "Windows-C," click "Settings" on the Charms bar and then click "Change PC Settings."
Click the "Search and Apps" side-tab, then click the "Defaults" side-tab.
Click on the current default email client under the Email section, then select the email client that you prefer from the drop-down list. Press "Alt-F4" to exit the Change PC Settings panel.
Internet Explorer 11
Press "Alt-X" to open the Tools menu, then click "Internet Options."
Click the "Programs" tab, then click "Set Programs" under Internet Programs. On the Default Programs window that shows up, click "Set Program Access and Computer Defaults."
Click "Custom," then click the radio button next to your preferred email client under the Choose a "Default E-mail Program" section. Click "OK" to save the changes.
Press "Alt-T" to open the Tools menu, then click "Options." On the pop-up box that appears, click "Applications."
Click the drop-down menu next to "mailto." Select your preferred email client from the list. In addition to any desktop email clients installed on your computer, Firefox also displays the Web-based email client Gmail as an option.
Click "OK" to save the changes.
To get Gmail functionality on Internet Explorer, you must download and install the Google Toolbar (see Resources). After installing, click the new wrench icon and select “Options.” Click the “General” tab, then check the box next to “Use Gmail for Mail to Links.” Click “Save” to set Gmail as your default email client on Internet Explorer.
Usually, changing the default email client from the PC Settings panel should automatically affect your Internet Explorer or Mozilla Firefox Web browser. If that does not happen, you must configure the Web browser directly.
By default, the Google Chrome Web browser uses the same default email client as set by the operating system. You can, however, configure Google Chrome to use the Web-based client Gmail as your default email application instead. Type "chrome://settings/" (without quotes) into your URL bar and press "Enter." Click "Show Advanced Settings," then click "Content Settings" under Privacy. Click the "Manage Handlers" button, then select your preferred client using the drop-down menu next to "mail:to." Click "Done" to save the changes. If you don't see the mail:to handler, sign into Gmail, then click the protocol handler icon. On the context menu, click "use Gmail," then "Done."