sending email to CSV list

Hello! What's the source of those users? Are they downloaded them from Braze and re-uploaded with additional data, or is it their first time in Braze? 

All that "0" in the Email column in the Reachable users section means is that these users cannot be messaged, because they're not subscribed or opted in. Can you do a user lookup using the user alias to see if the email addresses are on the user profiles in Braze? 

Two scenarios here:

1. Email addresses are missing in Braze. In this case, check if there are any errors on the user profiles. You might need to do a re-upload using external_id, considering the fact that these users are identified (since you have their email addresses already). Also try looking up the users using the email addresses from the CSV - make sure that the emails didn't create identified users and left these anonymous user profiles with the aliases - orphaned. 
2. Email addresses are not missing in Braze. In this case, if you're sure that these users qualify for receiving email campaigns, and if you can't message them even though the email addresses are in Braze, you need to update the consent. In the CSV, you can add another column named "email_subscribe" and set the value to "subscribed".
   
   

Let me know if this helped.