A business can only initiate a conversation outside of an active customer care window by using a notification. Notifications can only be sent using a predefined message template. Sinch registers these message templates with WhatsApp for approval. Once the message template has been approved by WhatsApp, the client can dispatch them using the API. Refer to the Sinch Documentation Site for details.
Each message template can include personalisation variables, which are defined in the onboarding worksheet. Sinch allows 250 such message templates to be created.