Send HTML email via C# with SmtpClient

How do I send an HTML email? I use the code in this answer to send emails with SmtpClient, but they're always plain text, so the link in the example message below is not formatted as such.

<p>Welcome to SiteName. To activate your account, visit this URL: <a href="http://SiteName.com/a?key=1234">http://SiteName.com/a?key=1234</a>.</p>

How do I enable HTML in the e-mail messages I send?

This is what I do:

MailMessage mail = new MailMessage(from, to, subject, message);
mail.IsBodyHtml = true;
SmtpClient client = new SmtpClient("localhost");
client.Send(mail);

Note that I set the mail message html to true: mail.IsBodyHtml = true;

I believe it was something like:

mailObject.IsBodyHtml = true;

IsBodyHtml = true is undoubtedly the most important part.

But if you want to provide an email with both a text/plain part and a text/html part composed as alternates, it is also possible using the AlternateView class:

MailMessage msg = new MailMessage();
AlternateView plainView = AlternateView
     .CreateAlternateViewFromString("Some plaintext", Encoding.UTF8, "text/plain");
// We have something to show in real old mail clients.
msg.AlternateViews.Add(plainView); 
string htmlText = "The <b>fancy</b> part.";
AlternateView htmlView = 
     AlternateView.CreateAlternateViewFromString(htmlText, Encoding.UTF8, "text/html");
msg.AlternateViews.Add(htmlView); // And a html attachment to make sure.
msg.Body = htmlText;  // But the basis is the html body
msg.IsBodyHtml = true; // But the basis is the html body

Apply the correct encoding of the Mailbody.

mail.IsBodyHtml = true;

i have an idea , you can add a check box to your project for sending email as html as an option for user , and add this code to enable it :

         MailMessage mail = new MailMessage(from, to, subject, message);

         if(checkBox1.CheckState == CheckState.Checked )
           {
               mail.IsBodyHtml = true;
           }

         SmtpClient client = new SmtpClient("localhost");

         client.Send(mail);

If you are using Mailkit,We can use TextBody,HtmlBody and Both for message body. Just write this code. It will help you

            MimeMessage mailMessage = new MimeMessage();
            mailMessage.From.Add(new MailboxAddress(senderName, [email protected]));
            mailMessage.Sender = new MailboxAddress(senderName, [email protected]);
            mailMessage.To.Add(new MailboxAddress(emailid, emailid));
            mailMessage.Subject = subject;
            mailMessage.ReplyTo.Add(new MailboxAddress(replyToAddress));
            mailMessage.Subject = subject;
            var builder = new BodyBuilder();
            builder.HtmlBody = "Hello There";
            mailMessage.Body = builder.ToMessageBody();            
            try
            {
                using (var smtpClient = new SmtpClient())
                {
                    smtpClient.Connect("HostName", "Port", MailKit.Security.SecureSocketOptions.None);
                    smtpClient.Authenticate("[email protected]", "password");

                    smtpClient.Send(mailMessage);
                    Console.WriteLine("Success");
                }
            }
            catch (SmtpCommandException ex)
            {
                Console.WriteLine(ex.ToString());              
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.ToString());                
            }