Only the first three characters are listed, corresponding to the Forward Sortation Area (FSA).
Canada Post provides a free postal code look-up tool on its website,[1] via its applications for smartphones, and sells hard-copy directories and CD-ROMs.
Many vendors also sell validation tools, which allow customers to properly match addresses and postal codes.
Hard-copy directories can also be consulted in all post offices, and some libraries.
There are no rural FSAs in Toronto, hence no postal codes should start with M0.