A new server machine was installed with Linux Operating system. The data were recovered from the crashed machine disks, and copied to a new server.  Only Inbox data were not recovered.

Special disks will be bought later and the data will be moved to the old server machine, which will have RAID and backup plan.

Discovered mismatched permission in the subfolders of most users. Script to modify permissions on subfolders was written & executed. Thereafter it was confirmed mailboxes are accessible.