UPDATE (10 December): The server which hosts /var/mail had a drive failure (one of the pins on the boot drive was bent, which short-circuited something and caused a system shutdown). We've restored the server using its other drive and are rebuilding RAID. All mail services should now be functional.
UPDATE (11 December): The mailspool server is down again, and its remote management system seems to be malfunctioning. Mail is down until an OCF staffer living in Berkeley can investigate; if the server is irreparably damaged, we'll have to wait until finals are over to rebuild it. Sorry for the inconvenience.
UPDATE (12 December): Some of you have expressed concern that your data may have been lost. Sorry for any alarm — rest assured, your data is safe, and we do have recent backups of /var/mail.
As part of our transition to a new mail infrastructure, we recently migrated /var/mail from our central disk array to a new machine with a better NFS server. We didn't realize until the server shut down two days ago that one of its drives was damaged, at which point we swapped out the drive and turned the machine on again. The server shut down again yesterday, and S.M.A.R.T. is predicting another drive failure, so we fear the motherboard or drive controller may have been damaged by the faulty drive. The server runs and your data is intact, but rather than just rebuilding RAID again and risking a major meltdown during finals week, we've decided to leave everything off after finals, when we'll have time to take care of this properly.
UPDATE (14 December): As of early morning today, mail is tentatively operational. Last night we transitioned /var/mail to an alternate hard disk in a temporary server. Maintenance work will be scheduled soon, especially over break. Special thanks to the ASUC for their cooperation.