Well, keeping in mind that, after all, we are speaking beta state here, one should not be too harsh about GUI. And this is what I find most faulty. Very rudimental, almost template like. Way too much white background and not very tactile for anything larger then 20" screens.
On 24" fullscreen seems like a lightbulb for my taste. But, I’m sure this is just temporary stage. Encryption seems to go greater lengths then most, and it seems to be the star attraction. Note on email aliases:
Pity since they offer a clever option for temporary aliases, where user can choose 15 minutes-2 weeks period., had they not expanded to "special domains" as well, rather then just Startmail.com. Something, for example, "15 minutes temporary email" service is doing.
I’m addressing and focused on web experience in my comments, while I will concentrate on client in next week, when I will have more time.
There seems to be many options, and I have a feeling, they will expand even more. Just using for day of two, so I can’t supply more data at this time.