Edit Sender and Bottom of Email Sent by Lead Generation Landing Page

I've just created our first Lead Generation Landing Page to allow subscribers to sign up to our newsletter. I would like to change the sender that appears when the "Thank You" email goes out. Additionally, I need to change the part of the email that appears below the dotted line, as it shows the wrong e-mail address. This is not the footer that appears beneath the entire email, but rather an auto-generated part of the thank you message that appears within the body of the message below a dotted line.