The process of changing the default email client on your Mac is not obvious and may seem a bit strange, but it’s easy to do. If you missed that opportunity, or the app never asked, you can set the default email client manually. Third-party email clients on the Mac may ask you, when you first run them, whether you want to set that email app as the default email client.
However, if you don’t want to use the Mail app as the default email client, you can use a different email app, such as Microsoft Outlook or Mozilla Thunderbird, and I’ll show you how.
The Mail app on your Mac is a decent email app and comes pre-installed and set as the default email client.