Both auto-forwarding and auto-reply are paid features, which makes cancelling & switching much more difficult. Gmail is a breeze comparatively. I highly recommend against using their addresses (e.g. protonmail.com, proton.me, pm.me)
Email forwarding is available for everyone with a paid Proton Mail plan.
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Thanks for the extensive response! You make some really good points and I was unaware of the political ick. Not sure if it’s enough to make me leave them because they do seem to at least handle the privacy aspect of their services correctly (for now at least), but those do seem like good areas that I’m going to watch more closely about them from now on.