A prior related topic was locked so I am starting a new one -"Not a Member"-2

I have actually had this happen twice in the last weeks - My own account and another account in my club.  We did not, to our knowledge, click the button to mark not a member.   
Is there a way to remove this option at the bottom of email sent out through Free Toast Host?  
 

You can remove the option - the setting is on the Email Security Tab of the Email & Contact Forms Module.  You can uncheck the checkbox labelled "Add "Not a Member?" Links to Emails sent to Members via FreeToastHost."
Note that some clubs seem to be reporting that they have this problem even without the checkbox active.