I think alot of people are becoming more interested in a blockchain based email services, i think the main issue is security. Whenever something happens, i.e keys or wallets stolen, in some cases its always big news and used to deter people from blockchain currancies and technologies on the premise that it is insecure. At the same time that it is not so simple to steal, a good chunk of people will still see it as to risky, especially in the case of entrusting incredibly sensitive material to it. They will not like the idea of "everyone has it, but only you have the key". Now, outside of the public domain.. the idea of emails being entirely accessible, as an example lets say when they ordered clinton to turn over emails.. What happened? OOOPS thousands got deleted. Lets say government officials and anything else that would require such a concrete system, this would have never happened and things cannot be hidden.
This leads to the potential for abuse, because afterall. All thats needed to access is the key, someone could use it to send an email from your address and from there they could do a number of things, like send something that would successfully incriminate your target.
Some things need to be tweaked a bit, but from afar, email and voting systems for SOME areas of life is in my opinion a leap ahead of the old methods and i can almost guarantee that employers or agency officials who need such demanding 100% oversight will be using such a thing in the not too far future