Aspose.Network for .NET v3.9.0.0 has released.

In this major release, we supported S/MIME protocol features. Now you can add a digital signature to your email message.

Here is the sample code:

   // load the certificate and associated private key from a file   
   X509Certificate2 certificate = X509Certificate2.LoadPfx("mycer.pfx", "password");

   // create an instance of MailMessage   
   MailMessage message = new MailMessage();

    // set its properties to desired values   
    message.From = "[](";  
    message.To = [recipient]([](;  
    message.Subject = "This is a signed message";  
    message.TextBody = "Hello, world!";  
    // attach a digital signature   

Download Link: