BLS strongly suggest to use the Purolator service. But I missed it and sent through Canada post for both mine and my spouse. They started to process my spouse's application and i can see that in the BLS website but my application showed as 'No records found'. I did called them and up front, I got the answer as ONLY Purolator service is accepted not any other. I stated my wife's application got accepted through the same 'Canada post' service and after couple of follow ups, they started to process mine as well. Now both of our status shows, "Processing at consulate general".
So once your canada post tracker shows it as reached, you need to call them and follow up to get it processed.