At 6:22 this morning, one of the hard disks in the University's IMAP server failed. This was automatically detected, the server immediately replaced the disk with a spare and started rebuilding the failed drive. No e-mail or other data will have been lost.
The failed disk is still in the process of rebuilding and will be for another couple of hours. As a result, users will find that access to their e-mail inboxes, both via the webmail client and via standalone IMAP clients such as Pegasus Mail and Outlook, is slower than usual.
Once the rebuild is complete things should return to normal.