Form IMM 1344, page 2 Box 1 reads:
-all correspondence with go to this address, unless you indicate an e-mail address below
-indicating an email address will authorize all correspondence, including file and personal information, to be sent to the e-mail address you specify
So if you entered an email address for yourself in the application (and you probably did, since you got your AOR on it), CIC is only going to email you with updates/documents. This also means that your approval should have been emailed to you as a PDF. e-Cas would still read that we have sent you a letter as it is a generic status. So if you don't see the letter by Feb 4th, call them and ask. Also, check your junk folders and such.