5 Recipient data
Some notifications can include data on the involved recipient. This can be just the ID of the recipient (property "recipient_id") or an additional set of profile fields (property "recipient_data").
The set of profile fields can be configured differently for each event type.
Tracking veto
Recipients can decide not to be tracked. In such a case, the recipent ID included in the notification data shows "not_tracked" and the "recipient_data" property is omitted.