/// <summary>
 /// Sends a single transactional email using send API v3.1
 /// </summary>
 public static Task <TransactionalEmailResponse> SendTransactionalEmailAsync(
     this MailjetClient mailjetClient,
     TransactionalEmail transactionalEmail, bool isSandboxMode = false)
 {
     return(mailjetClient.SendTransactionalEmailsAsync(new[] { transactionalEmail }, isSandboxMode));
 }