I have custom lists in SP2013 which I have created workflows to send email notifications to specific users.  My list displays an end-to-end view of an appeal which may be processed through 3 levels (with different users getting involved based on the level).  My issue is that I want the already sent emails to stop as the stages progress, but I continue to receive a duplicate email as the previous stage field is filled out (triggering an email).  Is there a way to pause those already sent emails from re-sending within a list item?

Note: I am new to Nintex and there seems to be no one within my company who can help guide me through this process.

Below is an example of my form.  When the initial appeal outcome is posted, an email is triggered.  When a response is provided within the form to that initial appeal outcome, another email is triggered BUT the initial appeal outcome posted email gets re-triggered.  I don't want that to happen.  Once the email goes out (regarding a single list item), I want it to stop.

I appreciate any help!

Katie