When importing users, the email attribute is required as stated by this knowledge article.
For you to be able to import these users, you would need to assign a dummy email as stated by the article in order complete the import.
However, when creating an user-imports job, there is a parameter called upsert. When this is set to true, an email is required. You can try passing it as false as seen in our documentation.
In the case of users which have their password hashed in a different algorithm than the standard one Auth0 uses, bcrypt), the custom_password_hash property will be required in the file.
You can read more about Bulk User Import Schemas here.
As an alternative, you can configure automatic user migration by configuring database action scripts in your connection. Please keep in mind that for you to be able to implement this, you would need to have a Professional plan active on your tenant.
If you have any other questions, feel free to leave a reply!
Kind Regards,
Nik