Not sure how many of you are aware of this but we have this thing out there called UMAPI which may be of use to you:
User Management API
This does use Adobe.io to get the connection going but its super useful:
Here is the diagram of how this works:
Getting Started with User Management
User Management API Documentation
User Management Walkthrough
Once this is all setup you can use this to update email addresses for users and usernames with ease. Using this method you can do multiple updates to a cloud without having to go to every single account.
Thought I would share this helpful nugget on how you can work with your cloud more effectively with the power of Adobe.io.
Kerry