Re: Not staying in system tray!
The reason the Thunderbird goes away is cause the extension is called "Minimize to tray". Which while the system runs it Minimizes it to the tray. It does not auto run Thunderbird at startup. You either have to add the Thunderbird executable to the Startup folder or find another extension for that. No email client stays in the tray after a restart.
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Phone: LG Optimus G Pro
Running: Stock JB from LG with Nova Launcher