Email Detective for Gmail: Identify ESPs & Check Authentication

See which ESP sent any email in Gmail. Detects 140+ 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 whether a shared or dedicated IP address was used. WHAT IT DETECTS: -140+ email service providers across marketing platforms, newsletter tools, CRM systems, and transactional email services -Detects Mailchimp, Brevo, HubSpot, Klaviyo, Salesforce MC and many more -Infrastructure providers like SendGrid and Amazon SES, with smart detection that shows the actual marketing platform when possible -HTML builders like Stripo and BeeFree FEATURES: -Instant ESP (email service provider) detection when you open any email -Clickable badge with ESP details popup -Email authentication checker (SPF/DKIM/DMARC) + BIMI and VMC -Shows whether it's a shared or dedicated IP (where it can be detected) -New: bulk scanner. Scan 50 emails at once -Works in inbox list view for previously opened emails -100% private: all data stays in your browser *How to audit your own deliverability in seconds*: -Send yourself a campaign from your own email marketing service. -Open it in Gmail and click the "Sent via" label. -You'll see SPF, DKIM, DMARC and BIMI status laid out cleanly. If something is missing or failing, the label will show a warning triangle. 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 personal data collected. Changelog: v1.8.11 Detects Gmail's "suspicious message" warnings. Fixes a Substack-detected-as-Mailgun bug. v1.8.7 -Minor housekeeping update with improved listing title for clearer discoverability. v1.8.6 -Adds Epsilon, CleverTap, and EcoSend detection. Renames eSputnik to Yespo. Detects Unlayer email builder. v1.8.2 -Fixes: improved Amazon SES detection. -Performance improvements (faster loading) v1.8.0 - New: report incorrect detections from the popup ("Wrong detection? Tell us") - Cordial, Smaily added - Better favicon handling for vendors whose apex domain has no /favicon.ico v1.7.30 -Added smarter ESP attribution by capturing sending subdomain info for SPF analysis v1.7.27 -Various bug fixes v1.7.25 -New "Broken authentication" chip when no ESP detected but DMARC/SPF+DKIM definitively fail -Fixed false ESP attribution from quoted reply chains (multi-line References leak) v1.7.18 -More ESPs added (Userlist, HubSpot Starter) -Fewer false positives on forwarded emails -Accuracy fixes for Marketo/Braze/Tabular/Mailtrap. v1.7.10 -New ESPs added: Bluecore, OptiPub, Sarbacane and User.com. -Bug fixes and security improvements v1.7.9 -HTML builders like BeeFree, Tabular and Stripo now also get detected -Fewer false positives, especially in replies and forwards -Favicons in the popup, cleaner layout -Stats no longer inflated by re-opening the same emails v1.7.8 New Settings tab with sign-out, cache refresh, and clearer privacy controls. v1.7.7 -Authentication warning indicator on emails with broken SPF/DKIM/DMARC. Shows a ⚠️ now in the label next to the subject line. -Reliability fixes for badge display in Gmail's list view. v1.7.6 -Better detection (120+ ESPs more reliable) -Smarter inbox tracking — same email isn't re-counted if you reopen it. -Detection of more technologies (e.g. AMP) v1.7.5 -More ESPs added (Kajomi, Optimizely Campaign) -Various detection accuracy improvements v1.7 -Bulk scan "Next page" works correctly in folders with 1,000+ emails (e.g. Trash) -Auth detection now scopes to the displayed sender on threads with forwarded messages -"Unsubscribe" badge label clearer -Various detection accuracy improvements v1.6.10 -New: One-click unsubscribe (RFC 8058) status shown for bulk emails. See if a sender meets Google/Yahoo bulk sender requirements -Bulk scan "Next page" works across more Gmail layouts v1.6.8 -Bulk scan "Next page" works across more Gmail layouts -"Unlock" buttons now respond instantly instead of feeling unresponsive -AWS SES IPs no longer flagged as shared/dedicated since PTR can't distinguish v1.6.5 Stability improved v1.6.4 -New: BIMI/VMC detection for registered users (also reflected in stats). Improved Shared vs Dedicated server detection. v1.6.3 -Improved DMARC statuses in the scanning window -Smaller detection improvements and new ESPs added v1.6.2 -Fix for a bug when the preview pane is enabled in Gmail v1.6.1 -Smaller bug fixes -Detection improved, more ESPs added v1.6 -Important new feature: bulk scanner (beta). Try it out and let us know how you like it! v1.5.1 -Fixing an issue with permissions (extension asked for permissions it doesn't need) v1.5.0 -Multiple new ESPs added -Fixes for forwarded emails and DMARC reports. v1.3.1 -Fixes false positives and adds a new ESP. v1.3.0 -New: now shows whether a sender is using a shared or dedicated IP address. This helps you understand the sending setup behind any email at a glance. -Perform a deeper IP reputation lookup by opening Talos (popup includes a direct link now) -Added more ESPs (Pipedrive Campaigns and Connectif) -Improved pattern matching for ActiveCampaign, Brevo, and CleverReach v1.2.3 -New ESPs: Added Seguno and Lettermint -Fixed: certain Braze customers were detected as SparkPost. -Fixed: False positive Iterable detection -About panel in the popup added v1.2.2 - Fixed false positives for 3 ESPs - Added/Improved detection for Iterable and Acoustic v1.2.1: Added Magnews and Inboxroad ESPs Improved detection for MailerLite, GetResponse, and Ghost Pro Reduced false positives in body scanning v1.2.0 New: ESP Collection tracker in the popup. See how many of the 100+ providers you've spotted so far Reduced false positives: body scanner now only uses tracking domains, ignoring editorial links to ESP websites Fixed Substack emails incorrectly showing as Mailgun Added new ESPs: Maileroo, Mailtrap, PHPMailer, Strato Infrastructure ESPs no longer override app-level detections