Attach An Email with an attachments to another email - asp.net

Question

So I know how to send emails with attachments... thats easy.
The problem now is I need to add an MailMessage, that has an attachment of its own, to a different MailMessage. This will allow the user to review things and take the email that is pre-made and send it if everything is ok.
I am not sure this will be the final work flow, but I would like to know if easy.
I see a bunch of software out there that is for money, the users getting these emails will be using an outlook client.
This would be deployed to a cheap shared hosting solutions, must be able to run in Meduim Trust!
I would prefer not to have to lic a 3rd party software, No $ :(
Any ideas would be awesome.

Answer 1

MailMessages cannot be attached to other MailMessages. What you will do is create an .msg file, which is basically a file that stores an e-mail and all of its attachments, and attach that to your actual MailMessage. MSG files are supported by Outlook.
For more information about the file extension, go here: http://www.fileformat.info/format/outlookmsg/

Answer 2

As Justin said, there is no facility to attach one MailMessage to another in the API. I worked around this using the SmtpClient to "deliver" my inner message to a directory, and then attached the resulting file to my outer message. This solution isn't terribly appealing, as it has to make use of the file system, but it does get the job done. It would be much cleaner if SmtpDeliveryMethod had a Stream option.
One thing to note, the SmtpClient adds X-Sender/X-Receiver headers for the SMTP envelope information when creating the message file. If this is an issue, you will have to strip them off the top of the message file before attaching it.
// message to be attached
MailMessage attachedMessage = new MailMessage("bob#example.com"
, "carol#example.com", "Attached Message Subject"
, "Attached Message Body");
// message to send
MailMessage sendingMessage = new MailMessage();
sendingMessage.From = new MailAddress("ted#example.com", "Ted");
sendingMessage.To.Add(new MailAddress("alice#example.com", "Alice"));
sendingMessage.Subject = "Attached Message: " + attachedMessage.Subject;
sendingMessage.Body = "This message has a message attached.";
// find a temporary directory path that doesn't exist
string tempDirPath = null;
do {
tempDirPath = Path.Combine(Path.GetTempPath(), Path.GetRandomFileName());
} while(Directory.Exists(tempDirPath));
// create temp dir
DirectoryInfo tempDir = Directory.CreateDirectory(tempDirPath);
// use an SmptClient to deliver the message to the temp dir
using(SmtpClient attachmentClient = new SmtpClient("localhost")) {
attachmentClient.DeliveryMethod
= SmtpDeliveryMethod.SpecifiedPickupDirectory;
attachmentClient.PickupDirectoryLocation = tempDirPath;
attachmentClient.Send(attachedMessage);
}
tempDir.Refresh();
// load the created file into a stream
FileInfo mailFile = tempDir.GetFiles().Single();
using(FileStream mailStream = mailFile.OpenRead()) {
// create/add an attachment from the stream
sendingMessage.Attachments.Add(new Attachment(mailStream
, Regex.Replace(attachedMessage.Subject
, "[^a-zA-Z0-9 _.-]+", "") + ".eml"
, "message/rfc822"));
// send the message
using(SmtpClient smtp = new SmtpClient("smtp.example.com")) {
smtp.Send(sendingMessage);
}
mailStream.Close();
}
// clean up temp
mailFile.Delete();
tempDir.Delete();