Add detail about feature availability
Add detail about feature availability

https://trello.com/c/3hqoh6LU/1398-emails-in-auth0

jeffreylees/docs,yvonnewilson/docs,jeffreylees/docs,jeffreylees/docs,auth0/docs,yvonnewilson/docs,auth0/docs,yvonnewilson/docs,auth0/docs