After changing the setting in my previous post, the greyed out portion now says "Yes" instead of "Cancel". So I can confirm that using pkh's instructions and the one in my previous post fixed my problem.
Hi, I had exactly the same problem and came across the below link from Symantec:
http://www.symantec.com/business/support/index?page=content&id=TECH160277
Problem
Respond with" field is greyed out when trying to set up automatic response ...