I didn’t see one in my initial install but I have since created the robots.txt file.
Thing is, I’m disturbed that Yahoo, Inktomi (one of their associated enablers), and oath.com (another enabler), are just unsubscribing users. This seems to me like malicious activity.
And since I have enabled the robots.txt file and someone actually does unsubscribe, what happens? I will ask yahoo. . .