SignedCms Cms = new SignedCms(new ContentInfo(messageData));
            CmsSigner Signer = new CmsSigner(SubjectIdentifierType.IssuerAndSerialNumber, new X509Certificate2(@"c:\serv.pfx", "123"));
            Cms.ComputeSignature(Signer);
            byte[] SignedBytes = Cms.Encode();

            ContentInfo content = new ContentInfo(SignedBytes);
            EnvelopedCms envelopedCms = new EnvelopedCms(content);
            CmsRecipient recipient = new CmsRecipient(SubjectIdentifierType.SubjectKeyIdentifier, this.certificate);
            envelopedCms.Encrypt(recipient);
            byte[] encryptedBytes = envelopedCms.Encode();

            message.To.Add(new MailAddress(provMail));

            MemoryStream encryptedStream = new MemoryStream(encryptedBytes);
            AlternateView encryptedView = new AlternateView(encryptedStream, "application/pkcs7-mime; smime-type=enveloped-data");
            message.AlternateViews.Add(encryptedView);

            getSmtpConnection().Send(message);