The Postal Museum had been formed in 1971 by Canada Post, and had received various kudos for it’s completeness, but now it will be broken up into various travelling exhibits, with some of it staying behind in Ottawa at the new museum.
If you want to see if your ancestor was a postmaster at Canada Post, go to Post Offices and Postmasters list at the Library and Archives Canada www.collectionscanada.gc.ca/databases/post-offices/001001-100.01-e.php
The Post Office was created as a federal department in 1867, and in early 1950s, cards were prepared by the Public Affairs Unit using the files and letter books on file. They were eventually turned over to the Library and Archives Canada, and put online so that we could use them today as a research tool. The records for the 1875-1902 have not survived.