solution

 public async Task<ActionResult<string>> GetUserInfo()

        {

            var client = new EmailClient("endpoint=https://com-service-nmb.asiapacific.communication.azure.com/;accesskey=6eIgegVgnogMKha3Elylm+17NYqIFSwJb+chnd0I780r85B510/3t4wqPM96pmtEZY5JxRLk4Hu/cEN/j0verg==");

            // Fill the EmailMessage

            // Add the Mailfrom Address 

            var sender = "Tran-alert@nmb.com.np";

            var subject = "Testing";

            var emailContent = new EmailContent(subject)

            {

                PlainText = "Test Email Content From Azure Communication Servie Integration with dot net core 6.0"

            };

            var toRecipients = new List<EmailAddress>()

            {

                new EmailAddress("softwaricanrajan@gmail.com")

            };

            var emailRecipients = new EmailRecipients(toRecipients);

            var emailMessage = new EmailMessage(sender, emailRecipients, emailContent);

            //await client.SendAsync(emailMessage);

            await client.SendAsync(WaitUntil.Completed, emailMessage);

            Console.WriteLine($"Email Sent. Status = {emailMessage}");

            return Ok("Success");

        }