Hello Nalin, sorry for any inconvenience that happened because of this.
There was a recent update on the Email Communication Services, where you cannot create a new MailFrom address or enable the engagement tracking if you are on the default throttling limit.
Can you please confirm if you are on the default throttling limit? If so, you can submit a request to increase the throttling limit as mentioned in the documentation here https://learn.microsoft.com/en-us/azure/communication-services/concepts/service-limits#email then you will be able to use the aforementioned features.