The server response was: 4.3.2 Service not available, closing transmission channel

Question

I am getting this error while sending email from my application. Can anyone suggest any solution.

Service not available, closing transmission channel. The server response was: 4.3.2 Service not available, closing transmission channel

Below is code.

string adminID = "[email protected]";
MailMessage msg = new MailMessage();
msg.From = new MailAddress(adminID);
msg.To.Add("[email protected]");
msg.Subject = "Sample Email";
msg.Body = "Hello ";
SmtpClient SmtpMail = new SmtpClient();
SmtpMail.Host = "basic.smtp.ttu.edu";
SmtpMail.Port = 25;
SmtpMail.Send(msg);

Boccherini

Answer 1

Got the solution for the issue. The Server was rejecting the request because this application didn't have write rights on that server. The code was perfectly fine, just it was permissions problem. Hope this helps someone!

Boccherini

1. I've never had any permissions issues using system.net.mail. 2. How would one get rights while testing on a dev box? – Keyte

You might need to add your IP address to the firewall for the exchange server. – Goulette

Answer 2

Please check whether the server which is sending the e-mail is whitelisted on the SMTP server or Exchange server.

I had the same issue and whitelisting it on SMTP server resolved my issue.

Cline

Answer 3

use SmtpMail.Dispose(); after every loop so new connection will be requested by the client.

Sadirah