Signals from mail you send, labeled with their limits.

Track image requests, link requests, and hosted documents from Gmail. MailSignal does not call an image load “read,” and it does not treat a Gmail send as proof of delivery.

• Open detected means an image was requested. Image blocking, caches, and scanners can hide or invent that signal.
• A shared pixel cannot tell which recipient caused the request.
• Ordinary attachments are not measurable. Hosted documents are.