Anyone using the free Email Detective Chrome extension contributes anonymous observations every time it identifies an ESP from email headers in their Gmail.
We only collect { sender_domain, esp, day }. No install ID, no email content, no IP, no link to any individual user. By design, we cannot reconstruct who subscribes to what.
Subdomains are rolled up to the organizational domain. Detections come from RFC-compliant header analysis, not body URL matching.
Email Detective is made by EmailTooltester. I'm Robert Brandl, EmailTooltester's founder, and I built it because I was always curious what companies actually use to send their newsletters. Now anyone can just look it up.