I assume you mean sign with S/MIME. You cannot. Netscape left it out of 6.0. I hear that they intend to put it back in 6.next. You can stick with 4.7 of Messenger (which is what I did) and wait for 6.next with S/MIME, or you can purchase an add-on product, although I don't know of any specifically that work with Netscape.
Have a question for an expert?
Please add a title for your question
Get answers from a TechTarget expert on whatever's puzzling you.