The first thing you should do is get to the point of the letter. However, keep it friendly. Most editors are already busy and working as fast as they can. Be sure to state the manuscript title and when you sent it to the publisher. Yes, you tell the address you mailed it to as well, especially if it's different from the address you're using for the inquiry letter.
Publishers do move from time to time because of expansion or mergers, among other reasons.
Try to always keep an inquiry pleasant. You'll get better results. Yes, you send them another SASE with the inquiry. You might have forgotten to include it and your address before and the publisher has been anxious to contact you. Your package might have suffered damage in the mail.