When creating a new user, we get this notification even though there is not another user with the same email. Am I missing something? We would like Netsuite to send an email for the user to set their password:

that means they have access in another netsuite instance, the credentials can be shared across multiple instances

They don’t thouogh. we just refreshed sandbox the other day and that is the only other environment

they could have access to another environment that is not related to your company

Ah… that would make sense. We are added the account for Oracle customer support

We've had this issue in two unrelated customer accounts. In one it related to access in a long forgotten Dev account. In another it related to an expired but not yet deleted Sandbox account.

Keep in mind it also does this if the email address has access via another customer centre portal (which might not be immediately obvious)