I lived in Canada last year. I did a NETFILE system through an online tax company, and it came up with an error. I tried again, and it still errored, but then returned me to the home page, where it says my return was 'printed and filed'.
This makes me uneasy, as at no point did they say 'yay, success' or anything along those lines.
Is there a way to check with CRA from outside the country to see if your return has been filed successfully? I'd hate to get stuck with a late filing.