You will need to read up on “ISINTEG”
The Microsoft Exchange Server information store cannot start if the globally unique identifier (GUID) for the information store does not match the GUID stored in the Windows NT Registry and the directory. This can occur if the Microsoft Exchange Server has been restored from an offline backup.
In patch mode, ISINTEG replaces GUIDs, resetting the entries in the database, directory and registry. It also patches information used in replication to prevent incorrect backfilling. This completes the restore operation and allows the information store to start again.
Hope this helps.