// creating the attachment
    System.Net.Mail.Attachment inline = new System.Net.Mail.Attachment(@"c:\\test.png");
    inline.ContentDisposition.Inline = true;
    // sending the message
    MailMessage email = new MailMessage();
    // set the information of the message (subject, body ecc...)
    
    // send the message
    System.Net.Mail.SmtpClient smtp = new System.Net.Mail.SmtpClient("localhost");
    smtp.Send(email);
    email.Dispose();

using System;    
    using System.Collections.Generic;    
    using System.Text;    
    using System.IO;    
    using System.Net.Mail;    
    using System.Net.Mime;    
    
    namespace devSmtp {    
    
    class Program {    
    
    static void Main(string[] args)
    {
    
    // This example show you how to send one email message with an INLINE attachment.
    // You can use this example also without the support of CDO or other type of SmtpClient.
    
    // creating the email message
    MailMessage email = new MailMessage("test@yourdomain.something", "test@yourdomain.something");
    
    // information
    email.Subject = "INLINE attachment TEST";
    email.IsBodyHtml = true;
    email.Body = "<div style=\"font-family:Arial\">This is an INLINE attachment:<br /><br /><img src=\"@@IMAGE@@\" alt=\"\"><br /><br />Thanks for downloading this example.</div>";
    
    // generate the contentID string using the datetime
    string contentID = Path.GetFileName(attachmentPath).Replace(".", "") + "@zofm";
    
    // create the INLINE attachment
    string attachmentPath = Environment.CurrentDirectory + @"\test.png";
    Attachment inline = new Attachment(attachmentPath);
    inline.ContentDisposition.Inline = true;
    inline.ContentDisposition.DispositionType = DispositionTypeNames.Inline;
    inline.ContentId = contentID;
    inline.ContentType.MediaType = "image/png";
    inline.ContentType.Name = Path.GetFileName(attachmentPath);
    email.Attachments.Add(inline);
    
    // replace the tag with the correct content ID
    email.Body = email.Body.Replace("@@IMAGE@@", "cid:" + contentID);
    
    // sending the email with the SmtpDirect class (not using the System.Net.Mail.SmtpClient
    class)
    SmtpDirect smtp = new SmtpDirect("localhost");
    smtp.Send(email);
    
    email.Dispose();
    }
    
    }    
    
    }