SslStream client unable to complete handshake with stunnel server
X509Certificate cert = new X509Certificate2(filename, password);
X509CertificateCollection certColl = new X509CertificateCollection();
certColl.Add(cert);

sslStream.AuthenticateAsClient(serverName);

SslStream sslStream = new SslStream(
  client.GetStream(),
  false,
  new RemoteCertificateValidationCallback(ValidateServerCertificate),
  new LocalCertificateSelectionCallback(SelectLocalCertificate));

sslStream.AuthenticateAsClient(serverName);

sslStream.AuthenticateAsClient(serverName,
  certColl,
  SslProtocols.Tls,
  true);

Element certificate is valid: False
Element error status length: 1

error 18 at 0 depth lookup:self signed certificate
OK