Interestingly, most postal workers are able to read.
So, providing your error is minor (eg K1A 0H4 instead of K1A 0H6 for example*) the postie who gets the item in his morning's work, will toss it over to his colleague who actually delivers to the written address.
A much much bigger problem would be an error in the street or apartment number.
Postal codes are used for a fairly preliminary sort.
*The former is the code for the Aboriginal Affairs Canada while the latter is the House of Commons.