One way to do this would be a custom “service” created with Automator. This application can be found in your Applications folder. Just create a new service with it (the cog icon), specify in the upper right corner that it is for Mail only and takes no input, then drag the mail action “New Mail Message” from the actions sidebar to the main field. Change the “from” field to your email address and save the service, e.g. “New Message (xyz@mail.com)”. There will now be an option in the Mail application under Mail > Services. Now you only need to assign a shortcut to it. In System Preferences > Keyboard > Shortcuts, look for your service and assign a shortcut. That’s it.