> Do you mistrust the unsigned emails from 10+ years ago because they were sent prior to DKIM?
Yes.
> As for authenticity, you could contact him, or his correspondents?
Correspondents aren't necessarily going to tell the truth about the authenticity of their own email. And that's assuming they're alive, reachable, and willing to talk, all of which may not be the case now and will be the case with 100% certainty in the future.
Yes.
> As for authenticity, you could contact him, or his correspondents?
Correspondents aren't necessarily going to tell the truth about the authenticity of their own email. And that's assuming they're alive, reachable, and willing to talk, all of which may not be the case now and will be the case with 100% certainty in the future.