Form validation not working
 

I am trying to create several Outlook task request forms that users
launch from a SharePoint library. I simply saved the .oft file to the
SharePoint library, and then asked users to open it from there. The
forms work fine, except I can't get the field validation to work. The
form is sent whether or not users complete fields marked required.
Here's an example of my simple validation:

Text field called ContentApprovedBy

Validation Formula:
[ContentApprovedBy] ""

Display this message if the validation fails:
"Value required. If not applicable, type'N/A, and explain in Notes on
page 1."

Any ideas or suggestions you have would be appreciated. Our company
does have an Exchange server, so if it needs to be published that way
instead of on SharePoint, we might be able to do that.