Information Needed On Cancellations

I have a number of covers on which I can only read a 6 digit number, stamped by the post office. I would like to know who to associate these numbers to any post office in the Country.

For example, how can I identified the post office associated to number 575984?

There must be a listing of these 6 digit numbers available somewhere.
I was unable to find any information through the Canada Post site.

Any help would be appreciated.