You may see this error message:
It is not possible to create this user, as another account exists with the same username.
How to fix it:
Contact the user’s previous employer and ask them to remove their account from Atlas.
Once removed, you can register the user with your company.
or
Enter a new username or e-mail for the user.
Many e-mail providers allow sub-addressing, often referred to as "the plus (+) trick" to add a tag (+tag) before the @ symbol of an e-mail address to create unlimited, functional aliases. E-mails sent to these addresses go to the main inbox, but can easily be filtered and identified.