If you click on an email address, the system will open an email application with a new email form addressee to the selected person. Your computer's default mail application determines which application opens. It is quite simple to change it to make Outlook the default application.
Windows.
Click the windows button and type ‘default’. In the list of programs, click ‘Default Apps’.
In the next panel, you will see the current default email application at the top. Click this (1) and then, in the list of available email applications, click Outlook (2). It should then work as expected.
MAC
Open the Mail app.
Choose Mail > Preferences, then click General.
Choose Outlook as the email app from the 'Default email reader' menu.