C# SMTP SendAsync not working

Question

I am having an issue using the SendMailAsync When I change it out for a normal Send it works fine. When I use SendMailAsync I get a connection has timed out and no mail is sent. Am I setting it up the wrong way?

edit: 1. I changed the variable name!!! 2.The exact error happens here await smtpClient.SendMailAsync(mailMessage); It just hangs until the connection times out, and I get an error description of "Connection has timed out" The status code returned is General Error

3. I'm calling the sendEmail from form the onClick event of a button for now. await unitOfWork.Instance.SendEmail(...) It's a single line of code in the onclick event

   public async Task SendEmail(List<string> notificationList, string emailSubject, string emailMessage)
           {
               var message = new MailMessage()
               {
                   IsBodyHtml = true,
                   BodyEncoding = System.Text.Encoding.UTF8,
                   Subject = emailSubject,
                   From = new MailAddress(FromEmailAddress),
                   Body = emailMessage
               };
   
                try
               {
                   foreach (var emailAddress in notificationList)
                   {
                       message.To.Add(emailAddress);
                   }
                   var people = string.Join(Environment.NewLine, message.To);
                   MessageBox.Show(@"from: " + unitOfWork.CurrentSystemUser.Person.Email + "To: " + people);
   
                   await SendMessage(message);
   
               }
               catch (Exception E)
               {
                ...
               }
               finally
               {
                 ...
               }
   
           }
   
       private async Task SendMessage(MailMessage mailMessage)
       {
           if (!CanSendSmtpEmail) return;
           await SendSmtpMail(mailMessage);
       }
   
       public async Task SendSmtpMail(MailMessage mailMessage)
       {
           SmtpClient smtpClient = new SmtpClient(SmtpClientHost, int.Parse(SmtpClientPort));
           smtpClient.SendCompleted += (s, e) => {
               smtpClient.Dispose();
               mailMessage.Dispose();
           };
           await smtpClient.SendMailAsync(mailMessage);
           //smtpClient.Send(mailMessage) works fine
       }
   

Answer 1

Increasing SmtpClient.Timeout won't work because it only applies to the synchronous Send method (see here).

Your code is working fine for me when I test it using GMail (like explained here) Can you give it a try with GMail or a different SMTP server? I think maybe your SMTP server is "acting funny". Also maybe you can show us how are you calling SendEmail method ?

Side notes:

1. Your question is really interesting (at least to me) but because of the way you wrote your code (property has the same name as method) people have down-voted it (you should fix that).
2. Also, can I see the full exception you get? (btw: catch (Exception E) - not good, use lowercase "e" for the exception argument name).
3. Make sure you understand exactly how asynchronous it really is.