I have a .net backend with react on frontend, when i click on a button from client side it should trigger an api that will put data in the db and then send an email. On local host everything works fine, i have followed the documentation from microsoft to configure azure. It has also a custom domain, but on the deployed web app with azure devops, it doesn’t want to send it, and i don’t understand what i miss and how can i fix it.

This is a part of my email service, and as i said, on local host works just fine.

        public EmailService(IConfiguration configuration)
        {
            var endpoint = configuration["EmailService:CommunicationServicesEndpoint"];
            var tenantId = configuration["EmailService:TenantId"];
            var clientId = configuration["EmailService:ClientId"];
            var clientSecret = configuration["EmailService:ClientSecret"];

            _emailSettings = configuration.GetSection("EmailService:AccountingDepartment").Get<EmailSettings>()!;

            var credential = new ClientSecretCredential(tenantId, clientId, clientSecret);

            _emailClient = new EmailClient(new Uri($"https://{endpoint}.communication.azure.com/"), credential);
        }

        public async Task SendEmailAsync(
            string subject,
            string htmlContent,
            List<string> toRecipients,
            List<string> ccRecipients,
            List<string> bccRecipients,
            string senderAddress,
            List<string> replyToAddresses)
        {
            var emailContent = new EmailContent(subject)
            {
                Html = htmlContent
            };

            var toEmailAddresses = toRecipients.Where(email => !string.IsNullOrWhiteSpace(email)).Select(email => new EmailAddress(email)).ToList();
            var ccEmailAddresses = ccRecipients?.Where(email => !string.IsNullOrWhiteSpace(email)).Select(email => new EmailAddress(email)).ToList() ?? [];
            var bccEmailAddresses = bccRecipients?.Where(email => !string.IsNullOrWhiteSpace(email)).Select(email => new EmailAddress(email)).ToList() ?? [];

            var emailRecipients = new EmailRecipients(toEmailAddresses, ccEmailAddresses, bccEmailAddresses);

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

            if (replyToAddresses != null)
            {
                foreach (var replyToAddress in replyToAddresses.Where(email => !string.IsNullOrWhiteSpace(email)))
                {
                    emailMessage.ReplyTo.Add(new EmailAddress(replyToAddress));
                }
            }

            try
            {
                var emailSendOperation = await _emailClient.SendAsync(WaitUntil.Completed, emailMessage);

                string operationId = emailSendOperation.Id;
            }
            catch (RequestFailedException ex)
            {
                throw new Exception("Failed to send email.", ex);
            }
        }

To change environment variables, to restart the app, change the build configuration.