Essential for Searching
Mailbox Indexing makes it possible to search for messages in the mailboxes based on content - until messages are indexed they cannot be searched.
Default = 'off'
Indexing is controlled on a mailbox by mailbox basis, with the default 'off' - indexing will not take place.
Set the System Default
The standard action is to use the system Default mode which is set from here:
Options | Server | Database-tab dialog.
Other options can be selected from the drop-down menus.
Only Index what you need
Each mailbox has two Indexing Modes which can be set independently; one for the mailslot and the other for the archive for the mail slot.
Indexing is resource intensive so it is normal to delay indexing until the normal Maintenance Period. If you select Index mail on arrival you will be able to search right away, but message storage and importing will be slower.
If the maibox never needs indexing then you should disable indexing to conserve resources.
Update This Index Now
There is also an option to force an index - selected from the dialog button [Update This Index Now]. Indexing will be reported in the Event Log and/or in Active Connections.
It is possible (and common) to have a mix of settings with most mailboxes on scheduled index, some on no index and say an Administrator mailbox set to index on arrival.
It is essential to configure the Archive to be Indexed if users are to be given the ability to search the Archive.