First,
If a Protonmail user emails a Tutanota user, it is NOT end-to-end encrypted.

Therefore,
Your solution of there already exists all these options is bullshit, because the options contradict each other.

Further,
It is unclear why a Nostr user, who promotes Bitcoin, (decentralized social media and money), would be opposed to decentralized email.

Finally,
I reject your entire worldview of having people self-host Bitcoin nodes, which add no value to their lives.
Yet, you dismiss people owning a VPS with their communications, emails, docs, files, ect.

Conclusion,
Given your complete failure to acknowledge basic facts, you're essentially spamming.  To say you're worthless would be an improvement, currently you are sucking up my resources to respond to low level dribble.  So fuck off and let's end this convo 

 You are a fucking idiot. Obviously It is encrypted If both people are on the same provider. Otherwise you can just import a PGP key and use it that way. 
The fact that you are telling people to self host but at the same time selling your own VPS solution as “self-sovereign” is exploitative. 
People will see through it and your “businesses” will inevitable fail
So fuck off and try scamming people somewhere else 

 It is not END to END encrypted unless the same provider.

Therefore:
You are promoting centralization.  Everyone on the same provider.