So all this has now been included. Just a small information on how it (should) work:
When someone types in his mail-address and hits "Subscribe", a mail gets send to the recipient defined in CSS/newsletter.php. This mail should than contain the following:
Add Email: "The address provided"
If someone hits "Unsubscribe", the content of the mail should be:
Remove Email: "The address provided"
For this to work, you'll have to set-up a SMTP-Server to handle these mails. Adding to that, it might be a good idea to set-up a solution of some sort which automates the "addition and removal" of the addresses to your address-book.
Have a nice day,