Any company large enough _will_ have to deal with compliance at some point, that's why most devs in large software companies have to take these silly "exams" every year telling you to not plug a USB key you found on the floor in your company laptop, even if it should be very obvious to most.
I'm seeing a lot of people here that are surprised by the fact that even a company who has privacy as their main marketing point has to deal with compliance, but really, unless you host your own mail server, you just can't guarantee your own privacy.
I don't generally advise hosting your own mail server due to all the troubles that come with it, but this is really one of the only ways I can think of where you can achieve a decent enough level of control when it comes to exchanging emails.