Send an Email via SMTP

SMTP stands for Simple Mail Transport Protocol and is a simple, well-defined protocol for exchanging emails with an SMTP server. Thankfully, the specifics of the protocol are handled for you in the System.Net.Mail.SmtpClient class. Figure 1 shows an SMTP client.

Figure 1. It’s very easy to create a simple SMTP client with full attachment support.

To see a full example of a simple email program, look at the EmailClient code example for this chapter. Here is just the method for sending email:

private void SendEmail(string host, int port,
    string username, string password,
    string from, string to,
    string subject, string body,
    ICollection attachedFiles)
{
    //A MailMessage object must be disposed!
    using (MailMessage message = new MailMessage())
    {
        message.From = new MailAddress(from);
        message.To.Add(to);
        message.Subject = subject;
        message.Body = body;
        foreach (string file in attachedFiles)
        {
            message.Attachments.Add(new Attachment(file));
        }

        SmtpClient client = new SmtpClient(host, port);
        //if your SMTP server requires a password,
        //the following line is important
        client.Credentials = new NetworkCredential(username, password);
        //this send is synchronous. You can also choose
        //to send asynchronously
        client.Send(message);
    }
}

					    

Note

The MailMessage class must be disposed after you send it. I once noticed strange problems with mail not going out immediately when I neglected to do this.