When using/creating "Responses" the user only has two fields:

• "Name" of the response
• "Response Text"

In practice, some users of a customer need some more fields like:

• To:
• CC:
• Subject:

All these fields should be optional. So the users can auto fill the subject because they very often have to send the very same answer to sometimes the same users (for whatever reason).

When there are already fields set by the user when the canned response is clicked, there should be a warning that these fields will be overwritten offering the user to either proceed or to cancel the application of the canned response.