MVC5 Mailkit send email with incorrect Email address - email

Question

I am trying to send emails using my MVC5 application. To do this, I have installed Mailkit v 1.22.0 through NuGet package manager. And this is how my code looks like:
var FromAddress = "no-reply#email.com";
var FromAddressTitle = "My Org";
var connection = ConfigurationManager.ConnectionStrings["SmtpServer"].ConnectionString;
var Email = new MimeMessage();
Email.From.Add(new MailboxAddress(FromAddressTitle, FromAddress));
var AddressArray = value.SentTo.Split(';');
foreach (var item in AddressArray)
{
Email.To.Add(new MailboxAddress(item));
}
Email.Subject = value.Subject;
Email.Body = new TextPart("html")
{
Text = value.Content
};
using (var client = new SmtpClient())
{
client.Connect(connection);
client.Send(Email);
}
return "Email Successfully Sent";
which works fine except if a wrong recipient Email address has been entered, the application does not detect if the Email was actually sent or not (client.Send(Email) returns void). Is there a way to know if it really ended up getting sent to the recipient or not? If it is not possible with Mailkit, is there any other NuGet package that can do this?

Answer 1

The reason that SmtpClient.Send() returns void is that the SMTP protocol does not specify whether the message gets delivered successfully. All it can do us tell the client that the messages was accepted by the server or not (in which case MailKit will throw an exception).
If you need to know whether the message was successfully delivered, you will need to check for bounce messages sent to you which could take minutes or even hours.
The first thing you'll have to do, however, is subclass SmtpClient and override the GetEnvelopeId and GetDeliveryStatusNotifications methods.
Then, when you receive a bounce message, the top-level MIME part will typically be a multipart/report (represented by a MultipartReport object when using MimeKit). This multipart/report will then contain a message/delivery-status MIME part (and possibly others), which will have a list of header-like fields that specify the details about the delivery status for 1 or more recipients.
MimeKit will parse a lot of this for you (e.g. it has a MessageDeliveryStatus class which contains a StatusGroups property that you will want to use. However, what MimeKit does not do is parse the individual field values (but they shouldn't be that difficult for you to do, typically a few Split(';')'s should be enough iirc for some quick & dirty parsing).
You will want to read the spec for this at https://www.rfc-editor.org/rfc/rfc3464
The MimeKit docs linked above specify which sections to look closely at (I think 2.2 and 2.3).
I would recommend looking specifically at the Original-Recipient and Action fields.
original-recipient-field =
"Original-Recipient" ":" address-type ";" generic-address
generic-address = *text
action-field = "Action" ":" action-value
action-value =
"failed" / "delayed" / "delivered" / "relayed" / "expanded"
You will also need the Original-Envelope-Id field to figure out which message is being reported on:
original-envelope-id-field =
"Original-Envelope-Id" ":" envelope-id
envelope-id = *text
The envelope-id text will be the same string returned by your GetEnvelopeId implementation in the SmtpClient class.