From looking through the source it doesn't look like it's possible to have optional mutual authentication. I have a requirement to allow TLS encrypted streams that are sometimes client authenticated with TLS and other times are authenticated through an additional authentication layer after tls negotiation is complete. I need to be able to allow mutual authentication and optionally include the cert in the CertRequestEventHandler, as well as optionally accept a null cert on the server side.

Thanks
JD

We've uploaded a new version of the library [v1.0.13.694] that does exactly what you need. Simply enable MutualAuthentication and set the verification type to Manual. If the client does not send a client certificate, the delegate will be called, but the 'remote' and 'chain' parameters will be set to null references.