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.
(source)


Thank you! Great answer!
For some reason, perhaps because I’m an absolute shill/sucker for free services, I always forget about mailbox.org. Thank you for bringing it to my attention and talking about its features!
Though, if I understand correctly, we basically don’t have a privacy-respecting email provider that offers auto-forward and auto-reply functionality in its free plan/tier: