S/MIME Emails

[g00fyman]

Hi all, Does anyone know of how to (or point me to some information on how to) send and email using X.509 PKI with attachments. There are a lot of posts around the Internet on using X.509 without attachments but it fails for emails with attachments. I would like to do this myself with native C# code and not use a third party product if possible. Thanks, Maurice