As of today Friday 7th February 2014 the Gmail Notifier is no longer supported by Google and will not check or notify you of new or read emails, it’s basically kaput. I am not privy to the reasons behind Google’s abandonment of the Notifier but I am guessing it’s because the code was old and protocols used defunct or not optimal.
Thankfully there are some good alternatives out there and I have tracked down and tired three of them.
ETA Google also has Desktop Notifications but I have not been able to get it working in Firefox, seems very buggy so I still recommend the apps below.
- Gmail Notifier Pro (free version or paid, lots of options)
- Gmail Notifier (nice basic email checker)
- Gmail Checker Chrome app (if you use Google Chrome web browser)
I will add more info as it becomes available.