SMTP : error relaying

Question

i am creating an email client that sends e-mail address from server ip instead of SMTP , i wrote that code:

SmtpClient server = new SmtpClient("50.23.128.66");
MailMessage msg = new MailMessage("from@yahoo.com", "tome@yahoo.com", "subject", "body");
server.Send(msg);

but when i run it , i get that error:

Unhandled Exception: System.Net.Mail.SmtpFailedRecipientException: Mailbox unavailable. The server response was: 5.7.1 Relaying Denied. at System.Net.Mail.SmtpTransport.SendMail(MailAddress sender, MailAddressColl ection recipients, String deliveryNotify, SmtpFailedRecipientException& exception)

* By the way i am using Windows Server 2008 * and i configured the smtp server to localhost and port 25 , but i don`t know what is that relying error .

When you send a `someone@foo.com` email through an `bar.com` SMTP server, you are using the `bar.com` server as a mail relay. If the `bar.com` server is not configured to relay mail, it will reject SMTP attempts that aren't part of its own domain, or users on it. In other words this is not a programming error, but a server error, and you should check with the server configuration. Perhaps better suited to serverfault.com. — Adam Davis, Jan 16 '12 at 18:59

score 3 · Answer 1 · answered Jan 16 '12 at 18:57

3

If you are using you localhost to rely email, you should be using 127.0.0.1 or localhost instead of that ip address you posted in your code.

answered Jan 16 '12 at 18:57

Icarus

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yes , but i have 3 ips on that server and i want to switch ips when sending emails , so that i dont be a spammer – R.Vector Jan 16 '12 at 19:08
2

Who said that by switching ips you won't be flagged as a spammer? It's more complicated than that. – Icarus Jan 16 '12 at 19:12

score 1 · Accepted Answer · answered Jan 16 '12 at 19:05

Relaying is the method the SMTP server uses to authenticate that it should route the email from a particular sender. An "open relay" means that there is no authentication and the SMTP server will send email sent from anyone. This is not a good practice and there are probably some mechanisms on this particular SMTP server to authenticates, such as a user name and password or even the IP address of the sender. Check with the administrator of the SMTP server to see what is required. I would think at a minimum you would need to set the user name and password, which you did not do in your code example.

SMTP : error relaying

2 Answers2