ITI Systems was notified that message queues were backing up on muexch04. It was determined that due to low disk space muexch04 was rejecting mail submission. The remaining 7 exchange servers were processing mail as expected. If any messages were rejected or delayed they should be retried shortly. We have corrected the low disk space issue on muexch04 and queues are behaving as expected. We will continue to monitor for 24 hours.