The server rejected one or more recipient addresses. The server response was: 503 This mail server requires authentication when attempting to send to a non-local e-mail address. Please check your mail client settings or contact your administrator to verify that the domain or address is defined for this server ..

7 Years
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Last Post by arunmozhi

Suppose the server's name is example.com It will allow you only to send email to xxx@example.com addresses. If you want to send email to @hotmail.com you need to have an account on the server, so you'll have to login with your email and password before being able to send. Is it your own server ? Then look in the manual, otherwise check your provider's support.


hi.. everyone.. the problem is solved..

Here is the Code..

private bool SendMail(string body, string subject)
        MailMessage message = new MailMessage();
        message.To = "name@domain.com";
        message.From = "name@domain.com";
        message.Subject = "Subject";
        message.BodyFormat = MailFormat.Html;
        message.Body = "Testing Message";

        string Username = "Username"; 
        string Password = "Password";
        message.Fields.Add("http://schemas.microsoft.com/cdo/configuration/smtpauthenticate", "1"); //none, cdoBasic, NTLM

        message.Fields.Add("http://schemas.microsoft.com/cdo/configuration/sendusername", Username);
        message.Fields.Add("http://schemas.microsoft.com/cdo/configuration/sendpassword", Password);

        message.Fields.Add("http://schemas.microsoft.com/cdo/configuration/sendusing", 2); // cdoNTLM, value 2. The current process security context is used to authenticate with the service.
        message.Fields.Add("http://schemas.microsoft.com/cdo/configuration/smtpserverport", 25);
        message.Fields.Add("http://schemas.microsoft.com/cdo/configuration/smtpusessl", false);
        message.Fields.Add("http://schemas.microsoft.com/cdo/configuration/smtpconnectiontimeout", 60);

        string SmptServer = "mail.domainname.com";
        System.Web.Mail.SmtpMail.SmtpServer = SmptServer;
        return true;

    protected void Sendthemail()
        bool y = SendMail(PanelToHtml(PanelMail), "Send Panel");
        if (y == true)
            ScriptManager.RegisterClientScriptBlock(Page, typeof(Page), "Msg", " alert('Current Mail has sent'); ", true);
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