There is an extensions to view (under Horde) the space used and free off email account logged with graph bar, but I don't found it ..

You have try this ?

thks

I don't know of anything to display a bar graph, but there is basic support built into IMP for quotas and a status bar shown at the top of the mailbox. You will need to configure the 'quota' option in your servers.php for IMP to properly obtain the qutoa of the user. This is non-trivial since only root can normally do this via the 'quota' command. It involves a) setting up sudo to allow it b) setting up your IMAP server to report quotas properly. Once you've got this configured, IMP should display the bar automatically. Modifying it to display a graph instead wouldn't be too difficult.