As far as getting the other end of the conversation, of course if I send it, it is now open for all to see. But if I have files uploaded to a server in Canada, then no, it is not available to the USA spies . Not that I have anything really to worry about, but I don't like the way the world is being harvested by the USA.
Not a big deal, but given the option to stay in Canada, I am going to take it.
That's why you being on a Canadian server isn't always going to mean you are totally safe. And that would also include files that you may have sent as well. Even meta data that's embedded in the email itself. A lot of stuff can be gleaned (header data could be hit or miss).
And it's quite possible that the company that you do business may have to (for whatever reason) use 3rd party servers etc. There is a lot of reasons, sometimes it's to take stress off while infrastructure is beefed up etc. How/where they do their backups of everything that's on their servers etc.
I'm not saying that is the case, just that it's something that could happen that may not sit well with you and usually these types of issues (and others) are covered in the EULA (and I know how much you love EULAs) typically not easily spelled out and under blanket statements.
If you are that concerned, self hosting is about your only option. Not always the easiest, but it's going to give you the most for your privacy concerns. Even at that isn't going to be 100% secure.
but I don't like the way the world is being harvested by the USA.
It's not just the US that does it.
Your PIPEDA as provisions in it that aren't the best with privacy of it's own citizens.
You have RIPA and Snoopers' Charter (this one I do believe is incompatible with European law) in the UK
Sweden has a law that allows for them to track sensitive words used in phone calls, faxes and
emails without court order.
Usually these things start off as a "protecting reflex", but amendments that come along later usually water things down.
What can I say, information is the new gold standard.