After using another much more rudimentary add on, this well written and continually updated add on is a pleasure to use.
Don't feel the need to go into specifics as it's all in the description, suffice it to say if you use Firefox and Gmail this is a must have add on.

I have used the Gmail Checker before, but now it is broken by changed in authentication process. I have installed this app and I really comfortable with it - i find the opening pop-up windows where you can manage your accounts and mails is really super!

The best extension I have ever used to manage Gmail accounts.
Five stars for sure!

This was the ultimate mail checker extension on Chrome and now that I've switched to Firefox, I'm very pleased to see that it's available here, too. However it doesn't work on Firefox 53 it appears. After setting up everything as usual, the icon shows an x in the upper corner and is greyed out. I can't even open the settings anymore. I only get an endless loading icon…

I have just switched over from Chrome to Firefox, and to my utter delight, I found out that Checker Plus is available for Firefox as well!

This extension is a must-have extension for anyone who uses Gmail to any degree. THe extension is intuitive, the layout/UI is efficient, and it is very hard to use a browser without it once you get used to it.

Of equally great import - the developed, Jason, is a thorough professional. If you have any trouble with his extension, be sure to email him or to leave your email address when you remove the extension from your browser. He WILL get back to you promptly, and he WILL fix your problem promptly.

Very Good! It fllow me from Chrome to Firefox. I it the best in same type plugins.

Very useful

My favourite mail notification extension from google chrome! So glad it's here on firefox now too.

Great addon!!

super cool

Easy to use, little to no technical problems. Interface is nice to look at and intuitive.

When I switched to Firefox 2 years ago this extension was the only thing I missed. I very nearly couldn't switch because this extension is so good. So glad it's here now. If you're looking for a gmail extension, look no further. All the others (and I tried EVERY one) don't come close to the ease of use found here.

if someone had a problem with the extension, it will not work as it should suggest:
1. Press the menu button New Fx Menu and then help
2. From the Help menu, select the Information for Technical Support
3. Press the Reset Firefox in the right upper corner of the page with information for technical support.

Jason, thank you for finally jumping on the Firefox boat. I'm one of those who donated for the Chrome extension, even though I didn't really need the extra features. I was desperate to ditch Chrome but for a long time the lack of this extension on Firefox prevented me from making the switch. That's how convenient it is.