When you change a user's email in Vincere, it works the same way as creating a new user, meaning that stats are not transferred and you will need to transfer ownership of profiles (candidates, contacts, job, company) from the old email address/user to the new one. It would be advisable to do it before the first of the month for reporting accuracy.
To detail the steps, You will need to go into the user management screen,
Select the user you want to change the email and deactivate the old user
Once you've deactivated the user, create a new user with the new email address.
Once you've created the new user, you can bulk transfer the profile's ownership to the new user.
Please note that you cannot transfer tasks and calendar schedules to the new user as these are linked to the email address they were scheduled with.
You can repeat this process for all the users that would require a new email to be registered in the system.