So, I hit their contact URL to tell them their auto-responder needs more brains. I wrote a polite note:
I received an automatic response from email@example.com for an email that I did not send. Normally I can filter such responses, but this one didn't have enough to identify it. I'd like to talk to an admin about how to improve the system you're using.
I submit to their form, and I get "internal server error." I tried it again as I was writing this, and it worked. At least, I guess it worked; it took me to their index page. I see it also sent me an automatic reply.
Software like this is what gives challenge/response a bad name. It's too bad. People see these things and think challenge/response is just a bad idea. It's like saying cars are worthless because the 1903 Fords lacked power steering.