Glenn's messages came from his account. I received one of them, initially thought it spam till the posts here, and then I associated the name. My mail server logs confirm it came from mail-wy0-f178.google.com, with a valid DKIM signature.

Glenn, if it helps, here is the message ID google assigned the spam I got.

AANLkTinr3c2wRePwJiKjknBtf1g53xAFjw5=-ibkwfyP@mail.gmail.com

From the header, it was sent via the web page, and not SMTP.