live@edu move to 365 have 3 domains only want to sync 1 domain

I have 3 domains root, mail(child), and adjunct(child). Root hosted by internal exchange, mail just moved to 360, and adjunct still on live@edu.

I am setting up fs 2.0 for mail and only want to sync mail not the root domain and not the adjunct domain. How would I do this? the admin on mail only has admin rights on mail and not root or adjunct.