When you click a link for an email address, your Mac opens the app you've set for that kind of link. Mail is the default email app. It works just fine for me. However, if you install other email apps, you might want to set them to open when you click an email link or web link. To set a default email app:
- Open the Mail app.
- If you haven't already set up an email account in Mail preferences or Internet preferences, follow the onscreen instructions to set one up now.
- From the Mail menu, choose Preferences.
- Click General.
- Choose your email app from the ”Default email reader” pop-up menu.
(This how-to is based on my experiences and info on Apple's support pages — where the images come from.)