Create a new @iCloud.com email address
Within iCloud settings, there is a tick box for Mail, which is switched off by default.
Ticking this box for the first time will invite you to create a new email address, ending in @icloud.com.
If you don’t want, or need another email address you can leave this unticked. Otherwise, go ahead and tick Mail. You’ll be asked to Choose an iCloud email address.
Follow the onscreen instructions to create your new email address. Once you’ve created your @icloud.com address, you cannot change it.
With the Mail feature ticked, the Mail application is automatically configured and ready to use with your @iCloud.com email address.
The Mail app is located in: /Macintosh HD/Applications
The best way to test any newly set up email account is by sending yourself an email. If the email sends, and arrives in your Inbox, you’ll know you can both send from, and receive emails sent to the account.