In general when someone mail their package it takes 2-4 days (depending on the courier service the person uses) to reach at CPC-V, and the only way (at this stage) to know if your package has been received is by using the tracking system of the courier company. ( so it is always better to use a postal/courier company who offers tracking and acknowledgement of the delivery).
Once CIC receives the application, the first step is to check the completeness of the application. if any important form is missing or the application is not complete (e.g missing signatures, sending incorrect forms, sending outdated forms..etc), in such a case CIC will return the whole application back. Only complete applications are put into further processing.
plz note that if the application is not complete and is to be send back then it takes 1-2 months to receive the application back.
Complete applications: applications which are complete proceed forward for processing. people on this forum had received acknowledgement letter from cic ranging from 1 week to 3 months. there are still some applicants here who had never received any acknowledgement letter and after many months they received AIP. ( i dont know if this a due to missing emails or wot). a large number of applicants also missed reading their acknowledgement email as it go into their spam emails. (so best is to mark cic emails safe in your email settings or regulary check your spam mails also). i have seen people here who had never received the acknowledgement but when they check their online application status they can able to see their status as "application received"
As far as you know your application is received by CIC then just relax, when you are dealing with CIC you need patience.
Hope it helps