The GnuPG crypto engine can deal with X.509 certificates and CMS messages needed for S/MIME emails. S/MIME can provide a nice user experience, if you accept the hierarchical trust model.

For it to work properly, you must go through the effort of properly setting up the root certificates. (This is technically harder than it could be (as of 2014-06), but the step itself is imminent to a hierarchical trust model.)

GnuPG 2.0

GnuPG 2.1

X.509 (last edited 2016-06-03 10:43:47 by bernhard)