Panel & Notifier for Gmail™ per Anthony

Panel & Notifier for Gmail™ is a Firefox addon that gives you access to Gmail (in mobile view) via toolbar panel window. Moreover, you will get badge notification for all new messages.

Note: Gmail is trademark of Google Inc. Panel & Notifier for Gmail™ is an unofficial addon and does NOT belong or relate to the official Gmail website or app at all. This addon is developed and maintained independently by its author.

Some Key Features:
a. Easy one-click access to Gmail via toolbar panel UI.
b. Supports most Gmail functions in mobile view.
d. Uses a very lite mobile Gmail user interface.
e. Gmail UI is free of all Ads and banners within the panel.
f. Addon's options page includes an option to adjust the Panel UI size (width and height).

Note 1: this addon only works with Firefox version 53.0 and above.
Note 2: if you want to report Bugs, please fill the Bug report form at the addon's homepage.