Gofame,
You have absolutely nothing to worry about.
I want to believe that the email address you're talking about is the one you wrote down in your initial application form to CIC in Nova Scotia. If you look at that application package again, you will see where it's written that filling an email address authorizes them to communicate with you thru the email as the preferred form of correspondence.
Your ecas will always display the P.O. box address, mine still does,even after "Decision made", and all the correspondence I got from CIC and AVO were all through my email.
The important thing to do, is to make sure you cannot miss any mail that comes to you. Check your email EVERYDAY. Never bulk delete, look through each mail to make sure it's not what you're expecting.
Sift thru your bulk, spam, junk mail boxes before you delete anything.
Someone had posted earlier about a gmail peculiarity that makes finding mails in the inbox a little difficult. Pls, check for that post and read thru, if you use gmail.
Thanks