在您的邮件服务程序中，可以使用异常捕获邮件失败

In your mail service program, the mail failure can be captured using exception

MailAddress from, to;
try
{
	MailMessage mailMsg = new MailMessage();
	.........
	SmtpClient smtpClient = new SmtpClient("mailserver", port);
	smtpClient.Send(mailMsg);
}
catch (IOException ex)
{
	MailMessage mailMsg = new MailMessage();
	to = from;
	.........
	smtpClient.Send(mailMsg);	
}

显然，退回邮件通知可以到达原始发件人.

Apparently, the bouncing mail notification can reach the originator.