This is interesting...just happened upon this at Canada Post's site:
Question
I received a Delivery Notice Card, but I was in all day. Why wasn’t delivery attempted?
You have received a Delivery Notice Card, but you have been in all day and did not see anyone attempt deliver.
When someone sends you a parcel, you always receive a Delivery Notice Card, and you are not aware of any delivery attempts being made.
You have received a Delivery Notice Card and want your parcel or letter to be redelivered.
Answer
We usually attempt to deliver all items directly to you, but in the following situations we leave a Delivery Notice Card instead:
If the item is marked as "card for pickup".
If you receive your mail at a community mailbox where your residence is more than 500 m from the mailbox, and the item does not fit in the parcel compartment.
Canada Post
My question is: Who is responsible for marking items as "card for pickup"...seriously?!