If the problems persist the server will be rebooted at Noon.
UPDATE
[2007-01-15 21:54:19 | Eric Fraser, IT Director]
IDSG has confirmed that the IMAP server troubles that have been seen since last week are continuing. There has not yet been a solution found to the trouble ticket that has been submitted with the vendor. The only known workaround is to shutdown one’s mail client (e.g. Thunderbird) completely and then restart it. IDSG is still working on the issue, but does not expect to get a reasonable solution until Tuesday.