Try something like this →
MailMessage theMailMessage = new MailMessage("from@email.com", "to@email.com");
theMailMessage.Body = "body email message here";
theMailMessage.Attachments.Add(new Attachment("pathToEmailAttachment"));
theMailMessage.Subject = "Subject here";
SmtpClient theClient = new SmtpClient("IP.Address.Of.Smtp");
theClient.UseDefaultCredentials = false;
System.Net.NetworkCredential theCredential = new System.Net.NetworkCredential("user@name.com", "password");
theClient.Credentials = theCredential;
theClient.Send(theMailMessage);
Well, based on your edit and additional information, I found this blog post by Jon Galloway , "Sending files via the default mail client . "
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