Implement DANE for added security and privacy
DANE (DNSSEC) would be hugely beneficial to the security and privacy of ProtonMail. DANE makes Man-in-the-Middle attacks practically impossible.
This is a necessary addition and should certainly be prioritized over-all, as it is at the core of what ProtonMail represents: privacy and security.
It's currently a feature available over at Tutanota (https://tutanota.com) and definitely sets it apart as an arguably more secure option, here's a great read on the topic: https://tutanota.com/blog/posts/dane-everywhere
Yeah, it's long overdue that Protonmail implements DANE. As you said Tutanota offer's it and so does Posteo. Both have had it for about 4 years now. More email providers need to get to work and add this, especially if your one that care's anything about secure email.
[Deleted User] commented
I absolutely agree, it'd definitely add to the security aspect of ProtonMail. It's not too big of an ask either compare to some of the other feature requests on here :P