Adding my email address -MacBook
By default, Xcode does not include your email in the automatically generated headers, regardless of whether you gave it to your Mac or not.

However, if you want to change how the automatically generated headers look, navigate to Xcode.app, right-click it, click on Show Package Contents, then go to Contents/Developer/Library/Xcode/Templates/File Templates. There you will find the templates Xcode uses; feel free to edit them to include your email address.

Note: the above assumes you have the latest version of Xcode, which is installed as an app, with the Developer directory inside the app bundle. If you have an older version, you'll probably find the templates in /Developer/Library/Xcode/Templates/File Templates instead.