what is the mistake? (sending email in asp.net)

Question

I am using this code for sending email in asp.net:

Using System.Net.Mail

public string SendEmail()
{
    SmtpClient obj = new SmtpClient();
    MailMessage Mailmsg = new MailMessage();
    Mailmsg.To.Clear();

    Recievers = new MailAddressCollection();
    Recievers.Add(txtToAddress.Text);
    SenderName = "Info";
    SenderEmail = txtFromAddress.Text;
    Subject = "subj";
    Body = "body";
    UseBcc = false;

    if (UseBcc)
    {
        foreach (MailAddress RecieverItem in Recievers)
        {
            Mailmsg.Bcc.Add(RecieverItem);
        }
    }
    else
    {
        foreach (MailAddress RecieverItem in Recievers)
        {
            Mailmsg.To.Add(RecieverItem);
        }
    }

    Mailmsg.From = new MailAddress(SenderEmail, SenderName, System.Text.Encoding.UTF8);
    Mailmsg.Subject = Subject;
    Mailmsg.SubjectEncoding = Encoding.UTF8;
    Mailmsg.BodyEncoding = System.Text.Encoding.UTF8;
    Mailmsg.IsBodyHtml = false;

    obj.Host = mail.domain.com;

    System.Net.NetworkCredential BasicAuthenticationInfo = new System.Net.NetworkCredential("info@domain.com", "password");

    obj.UseDefaultCredentials = false;
    obj.Credentials = BasicAuthenticationInfo;

    Mailmsg.Body = Body;
    Mailmsg.IsBodyHtml = true;
    try
    {
        obj.Send(Mailmsg);
        return "sent";
    }
    catch (Exception ex)
    {
        return ex.ToString();
    }
}

It correctly sends emails to recievers which are defined in my domain (like mail@domain.com), but I cannot send email to other mail servers (like mail@yahoo.com).

What is wrong in my code?

(May it relate to SmtpClient properties? I have set smtpclient.host to mail.mydomain.com and use username and password of one of my mail accounts which are defined in my domain)

Thanks

Does it throw any exception? Did you check with the SMTP server administrators (have they blocked your program on the SMTP server to prevent sending it outside?) — Sachin Nayak, May 17 '12 at 05:02
Yes the exception is: System.Net.Mail.SmtpFailedRecipientException: Mailbox unavailable. The server response was: No such user here at System.Net.Mail.SmtpTransport.SendMail(MailAddress sender, MailAddressCollection recipients, String deliveryNotify, SmtpFailedRecipientException& exception) at System.Net.Mail.SmtpClient.Send(MailMessage message) at _Default.SendEmail() — El Ma, May 17 '12 at 05:07
can you check the property "FailedRecipient" on the exception SmtpFailedRecipientException. Are you sure that is a correct recipient address? — Sachin Nayak, May 17 '12 at 05:14
@EIMa: make sure whether you are getting correct sender email format: txtFromAddress.Text. — Ashwini Verma, May 17 '12 at 05:33
I fill txtFromAddress with "support@mydomain.com" or "info@mydomain.com" — El Ma, May 17 '12 at 05:40
I would suggest that you try out that smtp server using a different email client, and talk to the smtp server administrators. the smtp server may not be knowing about any outside domains, and may be incorrectly configured — Sachin Nayak, May 17 '12 at 05:58

score 5 · Accepted Answer · edited Apr 13 '17 at 12:13

It must be something related to your exchange server. there are transport rules in exchange which define how you can communicate with the outside world.

http://www.msexchange.org/articles_tutorials/exchange-server-2007/management-administration/restricting-users-send-receive-external-messages-exchange-server-2007.html

you must be getting some exception while sending email to outside network

System.Net.Mail.SmtpFailedRecipientException: Mailbox unavailable. The server response was: 5.1.1 User unknown
   at System.Net.Mail.SmtpTransport.SendMail(MailAddress sender, MailAddressCollection recipients, String deliveryNotify, SmtpFailedRecipientException& exception)

If this is error you are getting this mean your exchange is not supported to send email directly to outside network. as I am no MS exchange expert but i have been using a exchange server configured in my network that can't send email to outside network but we enable email forwarding to contacts.

May be this can help you. http://www.petri.co.il/configuring-exchange-2007-send-connectors.htm

also i would suggest you share this problem on https://serverfault.com/

yea, I just want to say that email sending to other domains may be blocked frm your exchange server.. — Nitin Sawant, May 17 '12 at 05:40

what is the mistake? (sending email in asp.net)

1 Answers1