We are migration users from database to Auth0 and we don’t have passwords
We know that we can import all users w/o password and then password reset link to all users .
But is there a way using identifier first approach that once username is verified , user will receive email for password set for first time , if password is set user will not receive email .
To answer the question of using Identifier First, you can not use that to find out if users have passwords or to send emails.
If you bulk migration of users you should have a list of all users without passwords and as you mentioned, and can send a password reset. This can be helpful because you can tell when a user doesn’t log in because they didn’t reset their password. You can then delete the users.
You can use automatic migration to have Auth0 create a user if they are not in Auth0 already based off of the legacy database connection without re-prompting the user for a username and password. Here is some documentation: Configure Automatic Migration from Your Database