As described earlier in this User Guide, Inboxes and Outboxes act as approval gates in your SAP system for all SAP changes moving through the landscape.
When a change reaches an Inbox, an approval email is sent automatically to the defined approver(s). The change will not import into the associated system until Inbox Approval is granted.
When a change reaches an Outbox, an approval emails is sent automatically to the defined approver(s). The change will not move out of the associated system until the Outbox approval is granted.
When an approval is performed, the configured ShiftLeft analysers for this control point are executed automatically, presenting any warnings on-screen for the approver.