Adding signed mail in netscape

[Robert Krueger]

I received an e-mail yesterday in Netscape (Linux) that had a special
tag attached that indicated it was not encrypted, but was digitally
signed, similar to the gnupg fingerprint.   On opening the security
pane, I see that Netscape uses it's own flavor of crypt algorithim, but
does allow you to use others, like PGP or Gnupg.   Has anyone used this
feature before in Netscape where they have added, and use regularly,
Gnupg to sign their Netscape e-mail?
If you have, could you explain the install procedure?

Thanks,
Robert