Embed image to email message in System.Web.Mail.MailMessage

Question

I want to send email using System.Web.Mail.MailMessage along with System.Web.Mail.SmtpMail class. I know that this is a deprecated class but using System.Net.Mail is not an option for me.

So far I am able to send html formatted mail but I am not able to embed image to my email while sending.

This is what I've tried so far;

private static void SendMailMethod(string mailServer, int mailServerPort, string userName, string password)
    {
        const string SMTP_SERVER = "http://schemas.microsoft.com/cdo/configuration/smtpserver";
        const string SMTP_SERVER_PORT =
            "http://schemas.microsoft.com/cdo/configuration/smtpserverport";

        const string SEND_USING = "http://schemas.microsoft.com/cdo/configuration/sendusing";

        const string SMTP_USE_SSL = "http://schemas.microsoft.com/cdo/configuration/smtpusessl";


        const string SMTP_AUTHENTICATE =
           "http://schemas.microsoft.com/cdo/configuration/smtpauthenticate";


        const string SEND_USERNAME =
            "http://schemas.microsoft.com/cdo/configuration/sendusername";
        const string SEND_PASSWORD =
            "http://schemas.microsoft.com/cdo/configuration/sendpassword";


        var mailMessage = new System.Web.Mail.MailMessage();

        mailMessage.Fields[SMTP_SERVER] = mailServer;
        mailMessage.Fields[SMTP_SERVER_PORT] = mailServerPort;
        mailMessage.Fields[SEND_USING] = 2;
        mailMessage.Fields[SMTP_USE_SSL] = false;
        mailMessage.Fields[SMTP_AUTHENTICATE] = 0;
        mailMessage.Fields[SEND_USERNAME] = userName;
        mailMessage.Fields[SEND_PASSWORD] = password;

        mailMessage.From = "abc@xyz.com";
        mailMessage.To = "abc@xyz.com";
        mailMessage.Subject = "Test mail:";
        mailMessage.BodyFormat = MailFormat.Html;

        var mailAttachment = new MailAttachment("E:\imageToEmbed.jpg");
        mailMessage.Attachments.Add(mailAttachment);
        mailMessage.Attachments.Add(new MailAttachment("E:\TestAttachmentFile.txt"));

        var htmlBody =
            "" +
            "" +
            " " +
            "" +
            "" +
            "" +
            "Following is an embedded image:" +
            "
" +
            "" +
            "" +
            "";

        mailMessage.Body = htmlBody;

        try
        {
            SmtpMail.Send(mailMessage);

            Console.WriteLine("Mail sent");
        }
        catch (Exception ex)
        {
            Console.WriteLine("Error:" + ex.ToString());
            throw ex;
        }
    }

This code sends email but instead of showing image, the mail shows small square with a cross in it. How can I embed this "imageToEmbed.jpg" to my email.

rene · Accepted Answer

You can't achieve that with the classes System.Web.Mail because that implementation abstracts the access to a lot of features of the underlying Collaboration Data Objects component.

Instead of using the wrapper offered by System.Web.Mail.Message you better switch to using the CDO COM object directly. Add a reference to Microsoft CDO for Windows 2000 Library from the COM tab in the reference dialog.

After that you can use the following code to create and send an html email with embedded images:

var cdo = new CDO.Message();
// configuration
var cfg = cdo.Configuration;
cfg.Fields[SMTP_SERVER].Value = "smtp.server.com";
cfg.Fields[SMTP_SERVER_PORT].Value = 22;
cfg.Fields[SEND_USING].Value = 2;
cfg.Fields[SMTP_USE_SSL].Value = true;
cfg.Fields[SMTP_AUTHENTICATE].Value = 1;
cfg.Fields[SEND_USERNAME].Value = "user@example.com";
cfg.Fields[SEND_PASSWORD].Value = "password";
cfg.Fields.Update();

cdo.To = "awesome@example.com";
cdo.Sender = "me@example.com";

// attachment
var cdoatt = cdo.AddAttachment("file:///E:/imageToEmbed.jpg");
//this is why System.Web.Mail can't embed images
cdoatt.Fields["urn:schemas:mailheader:content-id"].Value = Guid.NewGuid().ToString("N");
cdoatt.Fields.Update();

// get a reference to out content-id field
var cid = cdoatt.Fields["urn:schemas:mailheader:content-id"];
// notice the special layout of SRC on the image tag, 
//it will be somethong like CID:123456789abcdef
cdo.HTMLBody = @"CDO
 ";

cdo.Send();

Notice how you can set the Content-ID header here on the Attachment. That is needed so you can use the Content-ID in the SRC attribute of your image.

A typical mailmessage will look

MIME-Version: 1.0
Content-Type: multipart/mixed;
    boundary="----=_NextPart_000_0001_01D1AF72.C8AE8C70"
Content-Transfer-Encoding: 7bit
X-Mailer: Microsoft CDO for Windows 2000
Content-Class: urn:content-classes:message
Importance: normal
Priority: normal
X-MimeOLE: Produced By Microsoft MimeOLE V10.0.10011.16384

This is a multi-part message in MIME format.

------=_NextPart_000_0001_01D1AF72.C8AE8C70
Content-Type: multipart/alternative;
    boundary="----=_NextPart_001_0002_01D1AF72.C8AE8C70"


------=_NextPart_001_0002_01D1AF72.C8AE8C70
Content-Type: text/plain;
    charset="iso-8859-1"
Content-Transfer-Encoding: 7bit

plain cdo 

------=_NextPart_001_0002_01D1AF72.C8AE8C70
Content-Type: text/html;
    charset="iso-8859-1"
Content-Transfer-Encoding: 7bit

plain cdo 
------=_NextPart_001_0002_01D1AF72.C8AE8C70--

------=_NextPart_000_0001_01D1AF72.C8AE8C70
Content-Type: image/png;
    name="file.png"
Content-Transfer-Encoding: base64
Content-ID: <42>
Content-Disposition: attachment;
    filename="file.png"

iVBORw0KGgoAAAANSUhEUgAAADQAAABLCAMA

Notice the Content-ID (here 42).

When using the plain System.Web.Mail classes your raw email will look like this:

MIME-Version: 1.0
Content-Type: multipart/mixed;
    boundary="----=_NextPart_000_0000_01D1AF70.59FC25F0"
X-Mailer: Microsoft CDO for Windows 2000
Content-Class: urn:content-classes:message
Importance: normal
Priority: normal
X-MimeOLE: Produced By Microsoft MimeOLE V10.0.10011.16384

This is a multi-part message in MIME format.

------=_NextPart_000_0000_01D1AF70.59FC25F0
Content-Type: multipart/alternative;
    boundary="----=_NextPart_001_0001_01D1AF70.59FC25F0"


------=_NextPart_001_0001_01D1AF70.59FC25F0
Content-Type: text/plain;
    charset="iso-8859-1"
Content-Transfer-Encoding: 7bit

Following is an embedded image:

  _____  

test afterit

------=_NextPart_001_0001_01D1AF70.59FC25F0
Content-Type: text/html;
    charset="iso-8859-1"
Content-Transfer-Encoding: 7bit

 Following is an embedded image:
test afterit
------=_NextPart_001_0001_01D1AF70.59FC25F0--

------=_NextPart_000_0000_01D1AF70.59FC25F0
Content-Type: image/png;
    name="file.png"
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
    filename="file.png"

iVBORw0KGgoAAAANSUhEUgAAADQAAABLCAMAAAAI0l

As you can see, there is no Content-ID header added and there is no code-path from the .Net implementation to add that header.

Embed image to email message in System.Web.Mail.MailMessage

Answers (2)

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