You just need to pass the list of recipient as comma separated in input box, else provide the single email for recipient.
Thanks
Manish Jawla
Create and manage Email Communication Service resource in Azure Communication Service
https://learn.microsoft.com/en-us/azure/communication-services/quickstarts/email/create-email-communication-resource
How to connect a verified email domain with Azure Communication Service resource
https://learn.microsoft.com/en-us/azure/communication-services/quickstarts/email/connect-email-communication-resource
Please provide the valid information for the below site properties:
Connection string from Azure
Sender email from Azure