Azure ATP - Sensitive Accounts

CyberSecGuy , there is no  official max number as we didn't put any max cap to it.

in theory you can run out of space in the config, but since there is no automated way to do so, you are unlikely to get to this point.

IF you need many accounts, the more practical Idea is to create a "sensitive" AD group, add all the accounts there, and mark the group as sensitive, this will eventually propagate to all accounts automatically.