Club members being changed to former members

Hello, sometimes me and other club members get unexpected emails asking us to confirm that we're no longer club members. Recently when this happened I checked the logs of the site and I didn't see that anyone had logged in to the site in the past few days. Why does this happen and how can it get stopped?

Please uncheck the option to Add "Not a Member?" Links to Emails sent to Members via FreeToastHost.  It's on the Email Security tab in the Email and Contact Forms module