Read by a human.
Not a robot.
Most read receipts lie. This one doesn’t.
What makes SentSonar honest
Machine opens are never “reads”
Proxies and scanners get their own badge — never a “read”, never a notification.
Unknown means unknown
Blocked pixel or ambiguous signal? The badge says so. We never guess.
Content stays in your browser
Our server sees one opaque token per message. Nothing else, ever.
Addresses never come back out
You see the network and the city — a /24, never someone’s exact address.
The four badges
The exact glyphs you’ll see beside your sent mail in Gmail.
- Tracked — Sent with tracking; no opens yet.
- Read — A human opened it.
- Machine only — Only proxies or scanners touched it. Not a read.
- Unknown — The signal was blocked or ambiguous. We don’t guess.
What SentSonar never does
- Never reads or transmits email content or recipient addresses.
- Never shows anyone’s exact IP address, and never stores browser fingerprints.
- Never uses the Gmail API or asks for OAuth scopes.
- Never runs analytics or loads third-party code inside Gmail.
Frequently asked questions
How does SentSonar track email opens?
When you send a tracked email from Gmail, the extension inserts a tiny invisible image (a tracking pixel). When the recipient's mail client loads that image, our server records the open — the same mechanism every email tracker uses. The difference is that SentSonar classifies each open as human, machine, or unknown, and never reports machine opens as reads.
Are read receipts from email trackers reliable?
Not by default. Apple Mail Privacy Protection pre-loads pixels on delivery, Gmail proxies every image, and corporate security scanners open everything. Most trackers count all of these as reads. SentSonar classifies them as machine traffic and says 'unknown' when the signal is ambiguous.
Does SentSonar read my email content?
No. Subjects, bodies, attachments, and recipient addresses never leave your browser. The server only ever sees an opaque random token per tracked message. SentSonar never uses the Gmail API and never asks for Gmail OAuth scopes.
Does SentSonar store IP addresses?
Yes, on our server, and it never comes back out. The address is what separates a provider's prefetch from a person, so we keep it with the open event — but the app only ever shows you the network it belongs to (/24 for IPv4, /48 for IPv6) and, when the fetch is the reader's rather than their mail provider's relay, a city.
Is SentSonar free?
Yes — free during early access. No account, no sign-up, no credit card.