I've recently started preparing a virtualised (Using Plesk/Virtuozzo)
web server with Courier IMAP. I'm noticing operations involving opening
folders are taking 5-10 seconds before anything seems to happen. This
happens when connecting via Thunderbird or by Squirrelmail which I've
installed on the server. I have access to another supposedly identical
web server and these operations are near instantaneous so it would seem
to be something set up differently between the two servers.