Compare
What commercial Gmail trackers ask for, and what this one does not.
A commercial tracker is a service you rent that reads your mailbox to do its job. MailSignals is a program you run that does the same job from inside the Gmail page. Most of the differences follow from that one distinction, and so do the two things it cannot do.
| Commercial Gmail trackers | MailSignals | |
|---|---|---|
| Gmail OAuth scope | Full mailbox access: read, compose, send and permanently delete all your mail | None. Sign-in asks for openid, email and profile |
| Google verification | Annual CASA security assessment; a 100-user cap until it passes | Not required |
| Where your data lives | The vendor's servers | Your Firebase project |
| Tracking domain | Shared with every other customer, and on blocklists | A subdomain of your own domain, serving nothing else |
| Cost | $3–6 per user per month, $36–72 a year | The software is free; about $0–3 a month to run |
| Source code | Closed | MIT licence |
| Why a tick is green | A tick | A classification, a confidence and a one-sentence reason, shown next to the verdict |
| Apple Mail Privacy Protection | Filtered out, or counted, silently | Labelled "delivered, open unconfirmed" and not counted by default |
| Your own opens | Rewrites the Sent copy through the Gmail API, plus heuristics | Correlates what you are looking at with the fetch; four paths, no API |
| Who opened a group email | Re-creates one message per recipient through the Gmail API and deletes the copies from Sent | Not offered. The tooltip says "N recipients, so we cannot tell which one" |
| Mobile app, Outlook add-in | Yes | No |
| Campaigns, mail merge, PDF tracking, e-signature | Yes, on higher tiers | No, by design |
| Mail sent by an AI agent through the Gmail API | Not tracked | Tracked through an agent key and an MCP server |
The commercial-tracker column describes the category as documented in vendors' own help centres and permissions pages: the full Gmail scope is what lets them rebuild group emails and rewrite the Sent copy. Prices are the published per-user monthly plans of the two best-known trackers when this page was written.
Why the scope is the whole story
A Gmail scope is a restricted scope. Google requires OAuth verification, an annual third-party CASA assessment, and caps an unverified app at 100 lifetime users.
Commercial trackers pay that price because their features need it. Rebuilding a group email into one message per recipient needs send and delete. Swapping the pixel out of your Sent copy needs read and modify. Exact reply detection needs read.
MailSignals declines all three and recovers what it can from the page instead: the extension can see what you are looking at, which thread just gained a message from somebody else, and which delivery-failure notice Gmail just filed. The result asks for nothing, and it is honest about the two places where "from the page" is weaker than "from the API".
Read what a Gmail scope really costs →As a Mailtrack or Mailsuite alternative
Mailtrack, rebranded Mailsuite in 2024, is the best-known Gmail tracker. The comparison is fair only if it includes what Mailtrack does that MailSignals does not.
What you give up
- Per-recipient tracking of group emails, which Mailtrack implements by re-creating one message per recipient through the Gmail API.
- Android and iPhone apps, a Gmail mobile add-on and an Outlook add-in.
- Campaigns, tracked PDFs, signature requests and video messages on the higher tier.
- A patented "debeaconizer" that replaces the copy in your Sent folder with a pixel-free copy through the Gmail API.
- A vendor to email when something breaks. Here the something is in your own project, with the specifications and decision records beside it.
What you get instead
- No Gmail scope. Nobody can read, send or delete your mail, because nothing was granted the ability to.
- Your data in your Firebase project, exportable as CSV or JSON, deletable for real.
- A tracking domain that belongs to you and has never been on a blocklist.
- A reason next to every verdict, and a "Who" line that says "the recipient, or you" when that is the truth.
- Self-open suppression that needs no API, plus tracking for mail an AI agent sends.
- Full history, link tracking, reminders and reports with no tier and no per-user fee.
Facts about Mailtrack are taken from its published help centre, permissions article and patent (US 10,749,835), as recorded in this project's pre-build research. They may have changed since.
And the sales suites
HubSpot Sales, Yesware, Mixmax, Streak and similar tools bundle tracking with a CRM, sequences and templates.
If you want the pipeline, they are the right tool and MailSignals is not trying to be one: there is no CRM, no sequence and no template library here, on purpose. If you want to know what happened to the email you actually wrote, without a subscription or a mailbox grant, the comparison above applies to them as well: they, too, need mailbox access to do what they do.
Run it in your own project.
One Firebase project, two subdomains, one deploy script. About an hour the first time, and no subscription afterwards.