When you are creating a new user account in Prospect CRM you cannot create the account without inviting the user.
Often you want users to be setup and to be able to assign them to accounts and test the system before you invite your users.
The way to resolve this at the moment is to use an email address that isn't used and then to update the email address when you are ready to invite the user and ask them to use the forgotten password link.
A better option would be to have a save/ create user option so that user accounts can be created and then when the account manager is ready they can invite users.