Whitelisting is optional. Callback security can be ensured using HMAC (a type of authentication to ensure that a Callback cannot be "Spoofed") signed Callbacks. These can be configured through the Sinch Dashboard.
Refer to the Conversation API Validating Callbacks section of the section of the Sinch Documentation site to learn more.
Learn more about Sinch Conversation API.
Watch this demo video to get a feel for how to make the most of connected conversations using Conversation API and the easily accessible demo on the Sinch customer dashboard:
The video shows you how you can get stared with Sinch using one simple API to reach customers over multiple channels and deliver a mobile-first experience that's out of this world.
Useful Links: