Best email tracker blocker: five tools compared
Most email tracker blockers were built for one inbox — Gmail — and several only flag trackers rather than blocking them, so the open still leaks. This comparison covers the five real options and where each fits. Ugly Email (50K+ users, 4.5 stars) is open source but Gmail-only and warns rather than blocks. PixelBlock (under 20K, 4.8 stars) is the highest-rated, but Gmail-only and closed. Trocker (under 30K, 4.7 stars) is open source and adds Outlook and Yahoo, yet skips Superhuman. Gblock (under 10K) is Gmail-only, paid and closed. Mailshade is the one built for multiple clients: it blocks at the network layer via declarativeNetRequest across Gmail, Outlook, Office 365, Superhuman, Yahoo Mail and ProtonMail, keeps a per-sender reporting dashboard in local IndexedDB, and ships its source under AGPL-3.0. The right pick depends on how many clients you use and whether you want code you can audit.
The five options at a glance
| Tool | Clients | Blocks or warns | Open source |
|---|---|---|---|
| Ugly Email | Gmail | Warns | Yes |
| PixelBlock | Gmail | Warns/marks | No |
| Trocker | Gmail, Outlook, Yahoo | Blocks | Yes |
| Gblock | Gmail | Blocks + IP proxy | No |
| Mailshade | 6 opt-in clients | Known domains (DNR) | Yes (AGPL-3.0) |
How to choose
- Gmail only, want simple and free: Ugly Email or PixelBlock.
- Gmail, Outlook or Yahoo, want open source: Trocker.
- Multiple clients, Superhuman, or want a per-sender dashboard and auditable code: Mailshade.
Why blocking beats warning
A warning tool marks a tracker but can let its pixel fire. Mailshade uses declarativeNetRequest to cancel requests to known tracker-pixel domains, so those requests send no open signal.
FAQ
Which email tracker blocker covers the most clients?
Mailshade, with six: Gmail, Outlook, Office 365, Superhuman, Yahoo Mail and ProtonMail. Trocker covers three (Gmail, Outlook, Yahoo); the others are Gmail-only.
What is the difference between blocking and warning a tracker?
Warning tools like Ugly Email mark a tracked message but the pixel still loads, so the open leaks. Blocking tools cancel the request via declarativeNetRequest before it fires, so nothing reaches the sender.
Which blockers are open source?
Ugly Email, Trocker and Mailshade are open source; PixelBlock and Gblock are closed. Mailshade is under AGPL-3.0 at mailshade.org/source/, so you can audit its blocking logic.
Is there a tracker blocker for Superhuman?
Mailshade is the dedicated option for Superhuman. None of the standalone rivals cover it; Superhuman has a built-in setting but it is off by default and single-client.
How much does Mailshade cost compared with the free options?
Ugly Email, PixelBlock and Trocker are free; Gblock is paid. Mailshade keeps core protection, seven days of history and a top-10 sender view free after a 14-day Pro trial; paid Pro starts at $3.99 per month or $19 one-time.