Thank you for your response! Allow me to provide further clarification. With the Email Communication Service, you have the option to add multiple custom verified domains using the "Add domains" feature.
However, when it comes to sending, managing, and tracking your emails in Azure Communication services, you can only connect and utilize one verified domain from your Email services resource.
So, 1 domain resource to 1 ACS resource is the current limitation. The motivation behind is to enforce boundary around each application domains that is used for communication.
Also, suggest you to send us an email with subject line “Attn:Sneha |thread title” to AzCommunity[at]microsoft[dot]com referencing this thread, I would like to understand better your usecase and solution on this.
Hope this helps.