Many services were offline yesterday, between about 8am and 3pm Pacific Daylight Time. Everything should be fixed now.
The cause was a filesystem glitch that caused one of the disks to behave like it was out of space, even when it should've had many gigabytes to spare. This prevented MySQL from running properly, which meant eventually DNS went down, and also caused problems for mail delivery (as new messages couldn't be created in home directories.)
It should all be fixed now, but if you encounter more problems, please let me know.
My apologies for the downtime.