This plug-in will allow you to collect email addresses on your website as well as sending text based emails to the entire list.  This is the light version and is limited to a small mail list. (Under 200 recipients.)

In order to send large campaigns of up to 20,000 you will need to upgrade to the pro version.  This requires a bounce removal account to handle the removal of bad email address.  The pro system reports email delivered, opened, and lists all users that followed links.