Registration documentation for every user

Hey mates,

so I just joined this company and took the responsability for it security.

Now, besides the usual password problems i noticed something very critical:

Every member uses it's company email adress to register onto different plattforms (i.e. google ads) and nobody takes note of where and when. So in the case of somebody leaving the company, nobody knows what he still has access to and what kind of information he can still get his fingers on.

Since i have to backtrack over 70 employees where they registered at and don't wanna mail everyone of them "Could you send me a list of where you are registered at?" (most of the time they won't even know), I wanted to check first if there isn't any tool or something similiar in Azure to backtrack it for every email adress?

Something comparable to googles "Third Party Access Management", even though we're not talking about "access".

And for the future: is there way to "control" where they are registering at?

And yes, every adress the employees are using is an Azure AD user.

Greetings

Benana