Our team uses Google Chat on Gmail. It would be good if you supported it.
(google chat notif on Checker Plus for Gmail)

https://support.google.com/chat/answer/9341104?hl=en&co=GENIE.Platform%3DAndroid

Being able to see my new emails at a glance without having to leave the current webpage I'm on in a huge game changer. Can't live without this now, thank you add-on dev!

Cet addon ralentit énormément Firefox lors de son démarrage.

Perfect mail notification extension, does exactly what is promised certainly when you contribute an amount you will have this fixed on most browsers.

I've been using this extension for, I don't know, how many years. At least 5, but probably more, and I love it.
There are a couple of things that this extension is missing on Firefox, though.
1. Shortcuts. Chrome's version has the ability to set activation hotkeys and some more. That's not the case for Firefox. As one of the many users who prefer keyboard-driven workflow, this feature is really missing. In fact, this is the only extension (out of 10) that forces me to use a mouse. I hope this feature will be added.
2. Auto dark mode. I can manually set the dark theme, but It would be nice if the extension could follow the system theme.
Other than that, the extension is really must-have.