Update opt-out-api-concept.md

Author: dbasantes

articles/communication-services/concepts/sms/opt-out-api-concept.md

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 ms.service: azure-communication-services
 ms.subservice: sms
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+[!INCLUDE [Public Preview Disclaimer](../../includes/public-preview-include.md)]
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 # Opt-Out management overview
 The Opt-Out Management API enables you to manage opt-out requests for SMS messages. It provides a self-service platform for businesses to handle opt-out requests, ensuring compliance with regulations and protecting customer privacy.
 Currently, opt-out handling includes configuring responses to mandatory opt-out keywords, such as STOP/START/HELP and others. The responses to these keywords are stored as part of program/campaign brief. The list of opted-out numbers is maintained in the Azure Communication Services Opt-Out database. This database management is automatic.