Writing email to the IIS Server's SMTP service pickup directory is another new feature of System.Net.Mail. The SMTP pickup directory is a special directory used by Microsoft's SMTP service to send email. Any email files found in that directory are processed and delivered over SMTP. If the delivery process fails, the files are stored in a queue directory for delivery at another time. If a fatal error occurs (such as a DNS resolution error), the files are moved to the Badmail directory.

By writing to the pickup directory, this speeds up the process because the entire chatting SMTP layer used for relaying is by passed. Below is an example of how to write directly to the Pickup directory.

[ C# ]

public static void PickupDirectory()
        {
            //create the mail message
            MailMessage mail = new MailMessage();

            //set the addresses
            mail.From = new MailAddress("me@mycompany.com");
            mail.To.Add("you@yourcompany.com");

            //set the content
            mail.Subject = "This is an email";
            mail.Body = "this is the body content of the email.";

            //if we are using the IIS SMTP Service, we can write the message
            //directly to the PickupDirectory, and bypass the Network layer
            SmtpClient smtp = new SmtpClient();
            smtp.DeliveryMethod = SmtpDeliveryMethod.PickupDirectoryFromIis;
            smtp.Send(mail);
        }

    Public Sub PickupDirectory()
        'create the mail message
        Dim mail As New MailMessage()

        'set the addresses
        mail.From = New MailAddress("me@mycompany.com")
        mail.To.Add("you@yourcompany.com")

        'set the content
        mail.Subject = "This is an email"
        mail.Body = "this is the body content of the email."

        'if we are using the IIS SMTP Service, we can write the message
        'directly to the PickupDirectory, and bypass the Network layer
        Dim smtp As New SmtpClient()
        smtp.DeliveryMethod = SmtpDeliveryMethod.PickupDirectoryFromIis
        smtp.Send(mail)
    End Sub 'PickupDirectory