I was trying to write a script which would add a new mail icon to my system tray, but apparently Thunderbird does not support checking for new mail from the command line.
I've tried a number of plugin, but they all seem to have only a vague description. The ones I tried just modified the new mail popup.
Therefore I'm looking for a plugin which displays an icon in the system tray for unread mails. It's not necessary to display the number of unread mails, but it would be nice though.
Best Answer
In the past I used this plugin: https://addons.mozilla.org/en-US/thunderbird/addon/firetray/
a quote from the official plugin page:
Worked perfectly as far as I can remember.