iCloud: Set up an @icloud.com email address
If you set up iCloud using an Apple ID that doesn’t end with @icloud.com, you must set up an @icloud.com email address before you can use iCloud Mail.
Note: If you set up iCloud using an Apple ID that ends with @mac.com or @me.com, you already have an equivalent address that’s the same except it ends with @icloud.com. You do not need to set up an @icloud.com email address to use iCloud Mail.
On your iOS device: Go to Settings > [your name] > iCloud (or Settings > iCloud), turn on Mail, then follow the onscreen instructions.
On your Mac: Choose Apple menu > System Preferences, click iCloud, select Mail, then follow the onscreen instructions.
After you set up your @icloud.com email address, you can use it to sign in to iCloud. You can still sign in using the Apple ID you used when you set up iCloud.