title: .NET SMTP.send not working but no errors
body: <p>I have a fully functional VB.NET solution working with a simple standard code i found in a lot of websites around the net, that is something like this:</p>
  
  <pre><code>    Dim oMessage As New MailMessage
      oMessage.From = New MailAddress("someone@abc.com")
      oMessage.To.Add("someone_else@abc.com")
      oMessage.Subject = "test mail"
      oMessage.Body = "test mail body"
      oMessage.IsBodyHtml = False
      Dim oSMTP As New SmtpClient("192.168.1.253")
      oSMTP.Port = 25
      oSMTP.EnableSsl = False
      oSMTP.Credentials = New System.Net.NetworkCredential("someone@abc.com", "password")
      oSMTP.Send(oMessage)
  </code></pre>
  
  <p>The working solution relies on the gmail smtp server with the usual configuration.
  I tried to replicate the same solution in another environment, where the smtp server is in the company LAN (192.168.1.253) and uses port 25, no SSL is required.
  The facts:
  1) the server I am trying to deploy my solution on is running a third-party software sending email from a dedicated address (I need to use the same email address). This functionality is active and working;
  2) I tried to connect to the SMPT server via telnet and I succeeded in sending an email to my private email address through SMPT protocol. This was expected, because the other software encounters no problem in doing the same job;
  3) I tested my solution, with try-catch block to get any error, but no email reaches the destination, even if my code terminates with no errors.</p>
  
  <p>I tried a lot of different options for smtp and message (and also with alternative destination addresses), but the result has always been the same: no message is sent. The last chance I have is to look for any conflict with server configuration or antivirus software. But I cannot realize why a "plain" dialog with the server through SMPT protocol is successful and my very simple code is not.</p>
  
  <p>Last note: the mail server i mentioned should be a Microsoft Exchange Server.</p>
  
  <p>Where could be the problem? Any help will be appreciated.</p>