On poor mail notifications and poor HTML support, those are strengths. Email is not a real time communication mechanism and most emails I receive I'd be happy to never be notified about, it's mostly just a deluge of unnecessary information. The same goes for html email, it's just an unnecessary intrusion into life from marketers obsessed with their branding over my convenience.
When everything on your phone and desktop is constantly seeking your attention it's nice to have some apps working for you.
I do support work for my small business via email, I need to know if a network is having problems, when a server goes down, if any users are having payment issues and jump in to fix these immediately if not sooner. A console ding as an email notification that I can't differentiate from pressing backspace one too many times is absolute trash.
Ideally I want Android-style reply in the notification level stuff.
When everything on your phone and desktop is constantly seeking your attention it's nice to have some apps working for you.