How to convert RTF to HTML email with embedded images and send it via SmtpClient 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:


To check this out first hand, unpack the archive and create a new C# Console Application named SmtpRtfToHtml. Next add reference to the “SautinSoft.RtfToHtml.dll” as shown on picture below:

How to add a reference to SautinSoft.RtfToHtml.dll

This is C# code of our application:

           using System;

using System;
using System.IO;
using System.Net;
using System.Net.Mail;
using System.Drawing;
using System.Collections;

namespace Sample
    class Program
        static void Main(string[] args)
            string pathToRtf = @"c:\Document.rtf";

            // 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 HTML email
            string from = "";
            string to = "";
            string subject = "This is a testing email from Bob to John using SmtpClient";

            MailMessage emailMessage = new MailMessage();
            emailMessage.From = new MailAddress(from);
            emailMessage.Subject = subject.Replace("\r\n", "");

            // 4. Attach images to email
            System.Net.Mail.AlternateView altView = AlternateView.CreateAlternateViewFromString(html, null, "text/html");

            foreach (SautinSoft.RtfToHtml.SautinImage simg in imageList)
                if (simg.Img != null)
                    LinkedResource lr = null;
                    System.IO.MemoryStream ms = new System.IO.MemoryStream();
                    simg.Img.Save(ms, System.Drawing.Imaging.ImageFormat.Png);
                    if (ms != null && ms.Position > 0)
                        ms.Position = 0;
                    lr = new LinkedResource(ms);
                    lr.ContentId = simg.Cid.Replace("cid:", "");

            // 5. Send the message using email account
            string userName = "bobuser";
            string userPassword = "bobpassword";

            SmtpClient client = new SmtpClient();
            client.Port = 25;
            client.DeliveryMethod = SmtpDeliveryMethod.Network;

            //client.UseDefaultCredentials = false;

            // Some smtp servers doesn't require credentials, therefore
            // you may set: client.UseDefaultCredentials = false;
            // and remove the line: client.Credentials = new NetworkCredential(userName, userPassword);

            client.Credentials = new NetworkCredential(userName, userPassword);
            client.Host = "";


If you need a new code example or have a question: email us at or ask at Online Chat (right-bottom corner of this page) or use the Form below:

Questions and suggestions from you are always welcome!

We are developing .Net components since 2002. We know PDF, DOCX, RTF, HTML, XLSX and Images formats. If you need any assistance with creating, modifying or converting documents in various formats, we can help you. We will write any code example for you absolutely free.