Loading certificate

        private SecureMimeContext CreateSecureMimeContext(string certificateFilename, string certificatePassword)
        {
            var secureMimeContext = new WindowsSecureMimeContext();
            var certificate = new X509Certificate2(certificateFilename,
                                                   certificatePassword);
                      using (var stream = new MemoryStream(certificate.GetRawCertData()))
            {
                secureMimeContext.Import(stream, certificatePassword);
            }
            return secureMimeContext;
        }