Condition split based of registered referrals?

If I connect a referral software to my store that allows people become a referral agent for me. Am I able to create a Conditional Split in my Post-Purchase Flow that would either send an email incentivising people to register to become an affiliate or skip that email entirely? 

Admittedly I don’t have this set up so I don’t know. But my guess would be that I have a custom property about the people who have joined my referral program stated as True. And then those who are labeled as False would get sent the email. 

Is any of this correct? please let me know. Thank you