The last big Gmail UI update broke it, but most of the ESP identification strategies probably still work: https://github.com/nquinlan/Email-Intelligence/blob/master/c...
Let me know if we can help.
The grandparent was worried about the extension stealing his email's contents.
I think the app store should warn that a page can send data to any website if it has permission to modify any page.
This is no more risky than any other extension whose permissions include `https://mail.google.com/`. Anecdotally, that probably includes most extensions seeing as how most of the ones I come across request `<all_urls>` whether or not they need it (not that that's okay).
In any case it's open source, so you can download it, audit the code, and install it locally to prevent auto-updating.
Yes, Gmail makes it harder than it should be to use the email client of your choice. But that's not a problem with email clients. That's a problem with Gmail. It's far from the only one.