I tried using the Gmail webapp and unity mail, but neither of them light up the notification indicator (the envelope does not turn blue). Unity mail doesn't even show up in the messaging menu. What can be done to fix them, what are some alternatives?
Mail Notification app works for me.
mail-notification works with system trays implementing the freedesktop.org System Tray Specification, such as the GNOME Panel Notification Area, the xfce4 Notification Area and the KDE System Tray.
I have tried unity-mail also, but no notifies at all. Tried with different accounts.
Unity Mail works fine in my case, on Ubuntu 14.04, with a Gmail account.
Actually it is the only one that works for me, among all other applications I tried (GMail Notify, CheckGMail, Main Notification, etc.).
It shows notifications for new mails both on Unity's System Tray (inside the mail icon) and on the Application Launcher bar. Simple but it does what it has to do.
You can try the Gnubiff notification app. You can directly install it from Ubuntu repositories. Once installed you can configure it as follows for the Gmail (replace the user with your Gmail username):