Protonmail for private email conversations

I wonder what you think about using a secure email provider like Protonmail for private, or generally confidential, emails. It would obviously most useful, if we decided to use Protonmail together. That way, our mutual email conversations would be encrypted by default. The following article explains why that’s not necessarily the safest option possible, but it would be convenient enough for most people to use:

Is anyone here already using Protonmail?