@lascapi @alternativeto IMO it's not important that you've got one tool that combines everything.
More important it that it is that flexible so that you can include/access/combine data and other tools as well.
Yes, #Emacs is probably *the* most versatile piece of software there is (and I'm using it since decades).
However, I don't use any of its built-in #email solutions (for reasons) but rather embed emails from my mail client (Evolution) so that I can link mails and open them very easily. That's the true power of advanced tooling, not the "one tool that does all of that".
And I'm aware of the irony of that message, considering the fact that Emacs has the power of including really anything(!) within its borders. 
And of course: it's always better when it's FOSS and not closed source in order to minimize #lockin effects (besides proper standardized, open storage formats).