I'm a tech idiot - can someone who has been here a while tell me whether these messages are credible RE: their authenticity?
Disclaimer: Everything I know about DKIM I learned within the last few days.
Essentially, you can establish a public cryptographic key on your DNS record (DNS is what maps a domain name to an IP address) so that anyone can look that up. You then use a private key and the public key, to "sign" the email. (In this case, I think google did that for them.) Anyone who wants to validate the email can use the public key (which they get from the DNS server) and the signature to check the signature. The message has to be exactly byte-for-byte identical to the one that was signed in order for the validation to pass.
Bottom line, it's a strong reason to think the emails are legit and untampered. The ones with DKIM signatures anyway, not all of them had that. I only validated a couple of them, and only at the validator that gntbs linked.
EDIT: I just tried a couple of the most recent ones and they didn't work. Here's one that does:
http://pastebin.com/RuK4AVhcI don't know enough about it to figure out what's wrong with the ones that don't pass.
@gawneedstobestopped -- how about just making a zip file of all the emails you've got?