I can say that we can use Canada Post. I always use them and it's fine.Do not use Canada Post. Use a courier service. I read somewhere that you should not use Canada Post. Yes, you can pay online and a receipt will be sent to you via email. Also, after payment, when the final page appears on your browser, you can save a pdf copy of the receipt locally and even send a pdf to any email address you want.
You can register your mail and you will get a tracking number and confirmation.
And it is way cheaper