Exchange 2010 Mailbox Database low disk space
This afternoon a customer contacted me, they were not receiving inbound emails but Outlook and outbound emails were working. I happened to be across the road so I went over to have a look. The Mailbox Databases were still mounted, the Hub Transport Server queues had errors and the inbound emails were waiting delivery.
It seems that once disk space for logs and/or databases gets below 1Gb Exchange cuts off all transport delivery to that database using logs on that volmues, this is to try to prevent running out of space.
In previous versions of Exchange administrators could tell when Exchange ran out of space as the Database would go offline and the logs or database drive would be full. Now with Exchange 2010 if you stop receiving email and the free space is below 1GB, Exchange willl have stopped transport delivery, this allows users to continue to access their mailbox and send outbound email by leaving the Databases mounted.
Once the free space is increased to over 1.5GB email transport will resume.