The changes you make to the email subject and message in this way aren't saved

The changes you make to the email subject and message using the Review Forms Before Delivery window will be used for the current email only, that is, the email you send when you click the Send Email button.

Once the window is closed, the changes you made won't be saved. For example, if you accidentally close this window before emailing, the changes are removed and the default text for the subject and message will appear the next time you open the window.

To make changes to the subject and message that will appear every time you open the window, you must enter the text in the Email Defaults window. (Entering default email subjects and messages for forms)