Email Detective

See which ESP sent any email in Gmail. Detects 90+ providers and shows SPF/DKIM/DMARC authentication.

Ever wonder which email marketing tool a company uses? Email Detective tells you instantly. Open any email in Gmail and see a "Sent via Mailchimp" (or Brevo, HubSpot, Klaviyo, etc.) badge right on the subject line. Click it for details: vendor website, authentication status (SPF, DKIM, DMARC), and a link to our independent review when available. WHAT IT DETECTS: -90+ email service providers across marketing platforms, newsletter tools, CRM systems, and transactional email services -Detects Mailchimp, Brevo, HubSpot, Klaviyo and many more -Infrastructure providers like SendGrid and Amazon SES, with smart detection that shows the actual marketing platform when possible FEATURES: -Instant ESP detection when you open any email -Clickable badge with ESP details popup -Email authentication checker (SPF/DKIM/DMARC) -ESP favicon and vendor website link -Works in inbox list view for previously opened emails -100% private: all data stays in your browser PERFECT FOR: -Email marketers researching competitors -Agencies evaluating client tech stacks -Deliverability specialists checking authentication -Anyone curious about the tools behind the emails they receive Built by EmailToolTester.com, the independent email tool review platform with 15+ years of testing experience. Free. No account required. No data collected.