CODEWITHSUNDEEP
c#emailattachmentsmtpclientmailmessage
michaeln
michaeln

Reputation: 1052

Attach mail to MailMessage

What I want to achieve:

Scan mails and attach relevant ones to a "summary"-mail.

My problem:

I can't seem to find any information about how this is done. When using for example Outlook you can simply drag and drop a mail into another message thus attaching it. I looked through the headers and found that it's basically the mail's content and attachments with their content types attached without further encoding. But attaching this data to a MailMessage via Attachment.CreateAttachmentFromString didn't work out either, the file was displayed as a regular file.

My current code:

var mail = new MailMessage(settings.Username, to);
var smtp = new SmtpClient(settings.SMTP, settings.Port);

// ...
// authentication + packing stuff into subject and body
// ...

foreach (var att in attachments) 
{
    Attachment attachment = Attachment.CreateAttachmentFromString(att.Text, att.Filename);
    mail.Attachments.add(attachment);
}

client.Send(mail);
client.Dispose();
mail.Dispose();

My question:

Can C# do this out of the box using some hack or are there libraries that support that?

Upvotes: 1

Views: 2237

Answers (2)

michaeln
michaeln

Reputation: 1052

Well, I found a way to somehow does what I needed. This solution is not the perfect answer, but it works almost as intended.

Warning

This solution requires currently Outlook installed as the mail needs to be attached as a .msg file. I want to repeat that this is not the right way to go, this method is way slower than any other solution but it works. I will further investigate soon.

But for now, here's my Extension class: 

using System;
using System.Net.Mail;
using System.IO;
using Outlook = Microsoft.Office.Interop.Outlook;

namespace MailAttachment
{
    public static class Extensions
    {
        public static string AttachMail(this MailMessage mail, MailMessage otherMail)
        {
            string path = Path.GetTempPath(),
                tempFilename = Path.Combine(path, Path.GetTempFileName());

            Outlook.Application outlook = new Outlook.Application();
            Outlook.MailItem outlookMessage;

            outlookMessage = outlook.CreateItem(Outlook.OlItemType.olMailItem);
            foreach (var recv in message.To)
            {
                outlookMessage.Recipients.Add(recv.Address);
            }

            outlookMessage.Subject = mail.Subject;

            if (message.IsBodyHtml)
            {
                outlookMessage.BodyFormat = Outlook.OlBodyFormat.olFormatHTML;
                outlookMessage.HTMLBody = message.Body;
            }
            else
            {
                outlookMessage.Body = message.Body;
            }

            outlookMessage.SaveAs(tempFilename);

            outlookMessage = null;
            outlook = null;


            Attachment attachment = new Attachment(tempFilename);
            attachment.Name = mail.Subject + ".msg";
            otherMail.Attachments.Add(attachment);

            return tempFilename;
        }
    }
}

Additional information

This solution requires you to delete the temporary file after you sent the mail. This might look like this: 

MailMessage mail = new MailMessage();

List<MailMessage> mailsToAttach = mails.FindAll(m => m.Date.CompareTo(otherDate) < 0);
List<string> tempFiles = new List<string>();

foreach (var item in mailsToAttach) 
{
    string tempFile = mail.AttachMail(item);

    tempFiles.Add(tempFile);
}

// smtp.Send(mail)

foreach (var item in tempFiles)
{
    System.IO.File.Delete(item);
}

Upvotes: 0

rory.ap
rory.ap

Reputation: 35260

You would probably want to just use the Attachment constructor that takes a file name:

Attachment attachment = new Attachment(att.Filename);
mail.Attachments.add(attachment);

Of course, this assumes you've saved the attachment already out to your file system somewhere.

You could also just use the attachment's content stream to avoid the overhead of saving each attachment to file first:

Attachment attachment = new Attachment(att.ContentStream, String.Empty);
mail.Attachments.add(attachment);

NOTE: the second argument to that constructor is the "content type", which, if left as an empty string, will be text/plain; charset=us-ascii. Refer to RFC 2045 Section 5.1 for more content types.

Also, see MSDN for more Attachment constructor overloads: https://msdn.microsoft.com/en-us/library/System.Net.Mail.Attachment.Attachment%28v=vs.110%29.aspx

Upvotes: 2

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