For quite some time, I was wondering if there are ways I could record forms of communication with, say, Facebook servers and have a plausible proof that a specific event (such as receiving a private message with given contents) actually took places. While I learned that I cannot record TLS session and use it as a proof that would be difficult to forge, I wonder if the DKIM-signed notification e-mails would work better.
In other words, if somebody sends me an e-mail and his server supports DKIM - do I have a reliable proof that this e-mail was sent by this person and is genuine? Are there any caveats?