@soatok I think you are missing part of the problem when it comes to email. Lots of moving parts and the need to get every one on bored. SMIMP like lots of other ideas when it comes to email(even ones not related to privacy in the lease) are basically DOA as the person proposing them suggests something and then meanders on off.
Getting something to work requires lots of support at all levels of the stack.
It is not a question of political will, but available dev time. Sure, you can write a system and tell the major ones to fuck on off and refuse to talk to them, but the big thing is finding enough dev time to all the fixes across the entire stack, which is not likely to happen sadly.
Also telling major providers to fuck off unless they are willing to play ball is not exactly with out presidence as well.
So would not exactly say a political problem, but one of dev time.
And frankly not one that is fixable as it requires a team that has a damn good understanding of C, C++, Perl, and PHP to even begin making a small dent and inroads.
And not once has any one ever said "Hey, lets fix this."... it is usually "Hey ass holes I have an idea and you should implement it while I fuck off".