We have exchange 2003 running on SBS 2003. For the past month, when we come in the morning the Exchange mailbox store is unmounted. When we mount it back, it mounts without any issues. I looked at event logs and could not find much. This happens for most days of the weeks and may skip a day or two per week, but it has created real problem. I had run isinteg on it about a month a go or so, but it did not help.