letter to canada..urgent

It depends on did you write the correct receiver address:
-If the address correct, it usually can (if no accident on the way)
-If the address have a little bit wrong, it can arrive Canada but not the receiver
-If you missed to write "Canada" or just write "Canada" but have no details address, sorry that it will not go to Canada

Non-delivery effected only against recipient information incorrect.
You may rest worry if you've written the best.

You don't need to provide a return address when sending a letter. But if the letter can not deliver for any reason, Postal Canada can never return the mail to you.

Try to establish your habit to write you return address at the front left top corner of the envelope. That will be easy to check the letter has both addresses.

Yes, but if the letter cannot reach to Canada
It will go to the garbage