In the order comment field on each fulfilled order, Shopify will add a text saying:
Smart Send sent a shipping update email to CUSTOMER NAME (MAIL@MAIL.COM).
Smart Send sent a shipping update SMS to CUSTOMER NAME (+45 12 34 56 78).
Both these notifications are send by Shopify and is edited in Shopify Settings - Notification.
Smart Send only adds the tracking to the fulfillment, which automatically triggers the 2 types of notifications from Shopify.
See Shopifys guide for Email notifications: Shopify Email Notification
See Shopifys guide for SMS notifications: Shopify SMS Notification
Contact Shopify: Contact Shopify