Courier IMAP (as with all the customer mail machines). The problem wasn't with IMAP itself. It's kind of hard to explain the problem without a knowledge of how our system works, but I'll try.... As many of you may know, user data is stored on file servers which are separate from the actual web and mail machines. Unfortunately, a messed up database entry caused one of the mount points on this machine to get screwed up on the mail machines. This affected about 370 users or so (out of about 28,000 on that group of mail machines).

This problem affected a small percentage of users on that group of mail machines, and has now been fixed for good. Obviously it's still ridiculous that it took so long for the problem to be corrected, and I apologize for that.