Using XFCE and want to watch your mail account from your panel?
Install XFCE4-mailwatch-plugin via Synaptic, or via sudo apt-get install xfce4-mailwatch-plugin
Once installed, right click on the XFCE panel > panel > add new elements, and add Mail Watcher to the panel.
You'll see a rather ugly, greyish envelope icon in your panel. Right click on it. Go to Properties and add your mail account.
In order to replace the grey envelope icons, download and unpack the "Mail Icons" file from this page. and unzip them to your preferred folder. Click on the envelope buttons in Mail Watcher Preferences, and choose the newly downloaded normal and new mail icons.
You will be alerted of new incoming mail by a yellow star on the envelope.