I share your frustrations about email authentication protocols and big
mail providers, hence my original thesis that maybe email is not an
ideal medium for public forums from a technical standpoint.
But I am not as cynical about SPF, DKIM, DMARC, I believe they're
worthwhile and we're definitely better off with them than without. The
alternative to not having any authentication methods is to maintain
manual whitelists for everyone which would produce an environment much
more hostile to independent hosters than the current one.
There's one big difference: with mail signature/encryption, it's mainly
the mail body you are protecting (against tampering/eavesdropping).
With DKIM it's a set of headers plus some portion of the body.
It makes sense to sign some of the metadata associated with the message.
For a widely used protocol it'd be a necessity.
Cheers,
monodev
