Remindee manages all the process from the popup display to the sending of the emails, so you have absolutely no coding to do. Sending from your own server is not proposed. However, you can set “date & time” as “unknown”
Yes, you can download email addresses of visitors who subscribed through a popup in your “Email” section, at any time. If you added a GDPR checkbox in your popups (i.e. opt-in permission to send email newsletters), your export will include