Evolution is a nice program with integrated mail, addressbook and calendaring; I have being using it for my personal e-mail for several years. But when it comes to my daily mail at work, where I receive and write hundreds of e-mails every day, and sometimes work remotely by ssh, I still prefer to use Mutt.
Mutt is fast, configurable and very powerful, but I always had missed a simple way of knowing the amount of read and unread messages in each of the mailboxes. Two days ago I discovered that Justin Hibbits and Thomer M. Gil had written a Mutt patch that implemented this feature.
The list of detailed features in the webpage is very clear:
- A sidebar with a list of folders on the left side of the mutt window.
 - Hide/Unhide the sidebar with a single keystroke.
 - Every line in the sidebar lists a folder with the total and new number of messages in it.
 - Optionally highlight folders with new messages.
 - Scroll up and down the list of folders and open the selected folder.
 - Configurable sidebar width and colors.
 - Configurable key bindings.
 
After installing the Debian GNU/Linux package and following the very simple Documentation of the webpage, the sidebar folder works perfectly.