[wdewind]

Yes there is a real lesson about the pragmatic impossibility of true decentralization in email. Specialization of labor is a useful thing, it turns out.

That being said: the fact that is a protocol and not a proprietary standard does have decentralizing effects that do provide a useful incentive check against providers, even if there are only a few of them. There is also a real lesson there too, that one I'll leave for the reader.