At the moment, users who are managing multiple separate sites have to use different usernames, but this means that notifications don't go to the actual email address because the one used to log in doesn't actually exist.
Also makes it difficult to reset passwords as a password reset link can't be sent as the email address being used to log in doesn't exist.
It would be really helpful and beneficial for users to have one login with their correct email address to access all sites individually.
Or at least be able to set the email address the same even if the username needs to be different for each site to ensure that any email notifications from the system are sent and received to the right persons.
Also, need to use MFA which isn't possible when the email address isn't real!