contact us quit working but I can resend previous contact us messages

I just noticed that my contact us is broken. it broke after 8/22/15, so I've missed a lot of potential sales.

But if I go to email archive I can successfully resend a previously sent contact us message.

Log shows this message

22-Oct-2015 13:19:07 America/Phoenix] ERROR: Failed sending email to: "[email protected]" <> with subject: "Website Inquiry from Benzbonz Quality Pre-Owned Mercedes Parts" (failed validation)

The example in the previous post was a test message that I sent with a known good email address. So maybe the email validation php got messed up somehow

DrByte replied in another thread,,,

"First quick fix I'd suggest is to go to Admin->Configuration->Email Options, and find the "Contact-Us Pulldown" settings, and blank-it-out, ie: leave it empty.
Then check whether those emails work properly again."

And Contact Us is now working thanks