"It’s quite likely that other, unauthorized folks, are touching your mail system more frequently than you with such a lax attitude."

This is complete nonsense. I cannot imagine that there is anything particularly magical that requires something other than regular security updates on any server.

Manual intervention is borne of changing requirements or broken things.

Why should an email server for a handful of users require a lot of manual intervention?

Could you explain where that magical unauthorized access to my systems should be coming from?

Really, you sound more like someone who has read some FUD marketing material than someone who knows how to write an exploit or has any other serious IT security expertise. I am pretty sure I never had any unauthorized access to my mail server in the last ~ 20 years that I've been doing this. Obviously, my system isn't immnune from exploitation, but neither are Protonmail's, and you are massively exaggerating the risk.

He clearly states who likely pays for spreading this FUD…