User New Message - visual verification code (aka CAPTCHA)

[Glamourgan]

We don't need a verification code for users to send messages to each other in our forum. How can I get rid of this option?  I do to the Admin tab and then where can I go to uncheck this box?  I can't find it. Hoping it is that simple.

[Ninja ZX-10RR]

All those settings are in Admin, Security and Moderation, Anti-Spam.
Or index.php?action=admin;area=securitysettings;sa=spam;