What do you mean by running through a form? You should be able to build all webpages and forms in a sandbox the same way you would in your production instance.
Everything should work except for the ability to send mass emails.
Thanks John and Jamie! - I figured it out. It turned out that when a sandbox was refreshed from production, the URL to the form was hard-coded and pointed to the form in production and not to the sandbox. Once I changed it out to point to the form in the Sandbox, everything worked. (Sorry it took a while for me to respond. I hadn't notice the notification icon had changed.) Everything seems to be working so far.