Insert To Address into body of email?

I’ve got an email template with an image in the signature and I want to append the recipients email address to the URL.

http://www.somewebsite.com/someimage.jpg?john.doe@gmail.com//www.somewebsite.com/someimage.jpg?john.doe@gmail.com

I can’t even get the email address to insert into the body of the message.

I tried $email_to_addrs_names but it doesn’t get replaced with a value!