How to create HTML email with embedded images from RTF and send it using Outlook in .NET C#

In this article you will find how to create a simple .NET/C# application which converts RTF document to HTML email with embedded images and sends it using MS Outlook programmatically.

Let’s make a C# code satisfying of these conditions:

  1. Acceptable for any .Net application: ASP.NET, Windows Forms, WPF, Console, Web Service, SilverLight etc.
  2. Works at 32-bit and 64-bit Windows machines.
  3. Compatible with .NET 2.0, 3.5 , 4.0, 4.5 frameworks and even higher if such will appear.

To make converting of RTF to HTML email with images at server-side we’ll use RTF-to-HTML DLL .Net library. It’s .Net component which will provides API to convert RTF to HTML with all images which we’ll get in a list after converting. We need these images extracted from RTF to further adding them into email as attachments.

To get the ball rolling, download the RTF-to-HTML DLL .Net component from here:


Further, please unpack the archive. We’ll need the file “SautinSoft.RtfToHtml.dll” from the package. Create a new C# Console Application named RtfToHtmlEmail. Next add references to the “SautinSoft.RtfToHtml.dll”, “Microsoft Outlook Library” and “Microsoft.CSharp” as shown on pictures below:

Reference to Microsoft.Outlook library

Microsoft.Outlook library

This is C# code of our application:

           using System;

using System.IO;
using System.Collections;
using Outlook = Microsoft.Office.Interop.Outlook;

namespace RtfToHtmlEmail
    class Program
        static void Main(string[] args)
            // This application converts RTF file to HTML email with embedded images
            // and send the email using Outlook

            // Here we'll specify settings variables
            string pathToRtf = @"c:\Book.rtf";
            // We need this folder to store image attachments temporary.
            // Images will be deleted after sending the email.
            string pathToStoreTempAttachments = @"c:\temp";
            string from = "";
            string to = "";
            string subject = "Testing message from Bob to John using Outlook";

            // 1. Convert RTF to HTML and place all images to list
            string rtf = File.ReadAllText(pathToRtf);
            SautinSoft.RtfToHtml r = new SautinSoft.RtfToHtml();
            r.ImageStyle.IncludeImageInHtml = false;
            ArrayList imageList = new ArrayList();

            // 2. After launching this method we'll get our RTF document in HTML format
            // and list of all images.
            string html = r.ConvertString(rtf, imageList);

            // 3. Create an instance of MS Outlook
            //Type outlookApp = Type.GetTypeFromProgID("Outlook.Application");
            //object objOutlookApp = Activator.CreateInstance(outlookApp);
            Outlook.Application application = new Outlook.Application();

            // 4. Create a new MailItem and set the To, Subject, and Body properties.
            Outlook.MailItem newMail = (Outlook.MailItem)application.CreateItem(Outlook.OlItemType.olMailItem);
            newMail.To = to;
            newMail.Subject = subject;
            newMail.HTMLBody = html;
            newMail.BodyFormat = Outlook.OlBodyFormat.olFormatHTML;

            // 5. Retrieve the account that has the specific SMTP address.
            // Use this account to send the e-mail.
            Outlook.Account account = GetAccountForEmailAddress(application, from);

            // 6. Attach images to the email using cid
            // And send the email
            foreach (SautinSoft.RtfToHtml.SautinImage si in imageList)
                string imageCid = si.Cid.Replace("cid:", "");
                string pathToImage = Path.Combine(pathToStoreTempAttachments, imageCid);
                Outlook.Attachment attachment = newMail.Attachments.Add(pathToImage, Outlook.OlAttachmentType.olEmbeddeditem, null, imageCid);
                attachment.PropertyAccessor.SetProperty("", imageCid);

            newMail.SendUsingAccount = account;
        public static Outlook.Account GetAccountForEmailAddress(Outlook.Application application, string smtpAddress)

            // Loop over the Accounts collection of the current Outlook session.
            Outlook.Accounts accounts = application.Session.Accounts;
            foreach (Outlook.Account account in accounts)
                // When the e-mail address matches, return the account.
                if (account.SmtpAddress == smtpAddress)
                    return account;
            throw new System.Exception(string.Format("No Account with SmtpAddress: {0} exists!", smtpAddress));


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