Anybody have any experience or ideas setting this up for use with MODx?
Has anyone had to do this?
It would help if you were a bit more specific about what you are trying to accomplish. Give an example and you would most likely get more responses.
Most mail encryption is usually handled by PGP or GnuPG (open pgp) while transport is done over TLS or SSL. You would have to create a snippet and leverage the appropriate PHP resource.