He says "For all the above tests(9 in total), I clicked 'send', and the page loaded with the form completely reset. There is no output or logs. Whatever I typed in was cleared and the page reloaded."
But I see the log... it appears below the form... maybe they didn't scroll down? I can move the log above the form. Without seeing the log he is assuming the FROM is set wrong, but you can see in the SMTP log that it does change.
I've moved the log to the top of the page instead of the bottom... Hopefully that will help them see the issue since they are still missing the point.