What I’m currently doing in order to check any new signups (and total forum user count) on my forum is using the link yourdiscourseforum(.)com plus /users. So you visit yourdiscourseforum(.)com/users. Additionally I bookmark this url on my iPhone in order to check up on my forum user stats when I’m away from my pc.
Getting an e-mail notification seems great if your getting a “reasonable” amount of new signups per day, so not in the hundreds. What I would prefer to see is a weekly update/stats report about your forum being automatically emailed to you.