The first thing you need to do is subclass SmtpClient like the example in the docs:
http://www.mimekit.net/docs/html/M_MailKit_Net_Smtp_SmtpClient_GetDeliveryStatusNotifications.htm
public class DSNSmtpClient : SmtpClient
{
public DSNSmtpClient ()
{
}
/// <summary>
/// Get the envelope identifier to be used with delivery status notifications.
/// </summary>
/// <remarks>
/// <para>The envelope identifier, if non-empty, is useful in determining which message
/// a delivery status notification was issued for.</para>
/// <para>The envelope identifier should be unique and may be up to 100 characters in
/// length, but must consist only of printable ASCII characters and no white space.</para>
/// <para>For more information, see rfc3461, section 4.4.</para>
/// </remarks>
/// <returns>The envelope identifier.</returns>
/// <param name="message">The message.</param>
protected override string GetEnvelopeId (MimeMessage message)
{
// Since you will want to be able to map whatever identifier you return here to the
// message, the obvious identifier to use is probably the Message-Id value.
return message.MessageId;
}
/// <summary>
/// Get the types of delivery status notification desired for the specified recipient mailbox.
/// </summary>
/// <remarks>
/// Gets the types of delivery status notification desired for the specified recipient mailbox.
/// </remarks>
/// <returns>The desired delivery status notification type.</returns>
/// <param name="message">The message being sent.</param>
/// <param name="mailbox">The mailbox.</param>
protected override DeliveryStatusNotification? GetDeliveryStatusNotifications (MimeMessage message, MailboxAddress mailbox)
{
// In this example, we only want to be notified of failures to deliver to a mailbox.
// If you also want to be notified of delays or successful deliveries, simply bitwise-or
// whatever combination of flags you want to be notified about.
return DeliveryStatusNotification.Failure;
}
}
This will tell the SMTP server to send you emails about the delivery status of each message that you send.
These messages will have a top-level MIME-type of multipart/report
with a report-type
value of delivery-status
.
In other words, the Content-Type
header will look like this:
Content-Type: multipart/report; report-type=delivery-status; boundary=ajkfhkzfhkjhkjadskhz
Once you parse the message with MimeMessage.Load()
, you can check if the Body
is a MultipartReport
with the expected ReportType
property value.
From there, you can locate the child part that is of type MessageDeliveryStatus
(typically the second part I think).
From there, you will want to check the StatusGroups
property (see http://www.mimekit.net/docs/html/P_MimeKit_MessageDeliveryStatus_StatusGroups.htm) - each HeaderList
in the collection will have information for a different recipient.
You'll need to read the RFC's listed in the StatusGroups docs to figure out what possible headers and values you will need to look for.