I'm using XFCE4-mailwatch-plugin on my notebook. Sometimes, the internet connection is not available, for example when the notebook is awakening from sleep mode. Plugin tries to check the IMAP mailbox - and when it is not possible to connect to server, it shows a red error icon. But this icon never disappear, even after next check of IMAP server, when the connection is possible again. I found just one way, how to get rid of this icon - to "Show to log" window.
This is a dupe of bug 4747, but I don't have permission to mark it as such.
*** This bug has been marked as a duplicate of bug 4747 ***