Everyone who desires their e-mail communications to be private – or at least difficult to next to impossible for anyone besides the intended recipient to read should really use PGP.
Wondering if PGP has a back door? Maybe but highly unlikely – see the FAQ:
Unfortunately it’s not super easy to use and it’s not free – but then again neither is privacy. And it can’t be used on public computers such at the library, etc. Actually the trial version becomes a free but more difficult to use version.