How to know whether I send the email successfully using System.Net.Mail

Question

I use C# to send email using System.Net.Mail.

But How can I know whether the email has been sent successfully or fail?

Answer 1

当然不是一个直接的答案，但这里有一篇来自Coding Horror的关于通过代码发送电子邮件的好文章，它解决了你的问题。

Answer 2

The simple answer is that if it's a detectable failure then SmtpClient.Send will throw an SmtpFailedRecipientsException (it will throw an SmtpException if there is a connection problem).

The long answer is that, for many reasons, you won't necessarily get an exception. This can be because your SMTP server is buffering the sends (or if you have it set to local iis or local directory), or simply because the SMTP server does not support returning those error codes.

Most advertising mailing systems track bouncebacks by setting a valid "from address" and monitoring the inbox for that account. Even that, however, is not foolproof (out of office messages, for example).

I would stick to catching exceptions and leaving the others. If you're not sure if emails are valid, maybe you should send users a code to have them validate their email address.

Answer 3

Considering Emails are fire-and-forget, this can be quite hard. Unless you get an exception, denoting a client-server communication issue due to wrong credentials etc, you have no means of knowing if a mail was sucessfully send (meaning: arrived at the addressee).

Answer 4

I've personally never come across an answer to this as there's not really a way you can grantee mail leaving your location is'nt going to get thrown away as soon as it leaves you. You could maybe try and check the sending mailbox for an NDR (none delivery report) but your not always granted to get one

Answer 5

If you mean sent successfully then as other posters say, if it cannot be sent then you will get an exception. If you actually mean recieved succesfully then that is an entirely different matter. SMTP simply does not have a mechanism to find out if the message has been recieved by the recipient, sometimes you will get an ndr if a server can't deliver other times you won't. You could try and do what spammers do and that is to put some kind of image link in your html email body with a unique identifier in the query string. That would allow you to link someone hitting the image url with the email. However that would only tell you the email had been read if the url was hit, it would not tell you that the email hadn't been recieved becuase the recipient might simply not have allowed images to be displayed in their email client.