Most contacts will be created through campaigns, all of which will assign that contact to a user or round-robin them to a selection of users.
This is a fallback for contacts created in DRIVE that do not come in through a landing page campaign (if they text in, or are imported without a user assignment, for example) and thus do not get assigned to a user.
By adding a single email address, unassigned contacts will be assigned to this user.
You can add multiple comma-separated email address to have lost contacts assigned through round-robin (ex: [email protected], [email protected], etc.)
Entered emails MUST be users in your account already, or they will not be added as a fallback assignment.