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SMTP: Use Delivery Notifications
If the server supports delivery status notifications (see ExtensionDSNSupported property), it is possible to ask the server to notify the message sender about message delivery status. The notification will be provided as a separate email.
Examples:
C#:
if (smtp.ExtensionDSNSupported)
{
// report about message delivery failure or delay
smtp.DSNOptions = SBSMTPClient.Unit.sdnFailure | SBSMTPClient.Unit.sdnDelay;
// return only message header to identify which message not delivered
smtp.DSNReturnType = SBSMTPClient.Unit.srtHeaders;
}
smtp.Send(msg);