How can I see user's email addresses in Insights?
The email address is not a displayable attribute within Insights. This restriction is setup as a security measure, as Insights is hosted by a third party. However, there is a drill in setting you can add to your report, so if you click the user ID, it should take you to the user's profile within Support.
If you export that list, you can extract those user IDs and use the API below to extract the email addresses: