|Can I subscribe someone to my contact list by having them send a blank email to me?|
You can't do that with the application but there is a different way. The application includes the ability to create a custom subscription form that you can add to your web site.
When your visitors fill out this form all of their details (including custom fields) are saved into your the application database. If you need to subscribe them automatically, you can use the hidden form approach.
You will also need to pre-populate the form fields. You can do this using PHP. If you're not sure how we're more than happy to show you if you get stuck - just send an email from the client area.