GPG and PGP Compatibility

[Conan Purves]

Hello everybody,

I am the office manager here and trying to set up a compatible PGP for
some of the employees.  I am looking for an open-source, free
non-corporate version of the software and have thus found Gnupg using
the gpg4win front end, running through the Enigmail extension on
Thunderbird.  We are using Windows boxes here.

I have succeeded in installing it and getting it to work.  However,
there have been many little details that prevent me from rolling this
out to the other employees.  My last problem, I believe, is attachments.
   I have installed gpgee which encodes and decodes attachments (as
there seems to be no function to do this in Engimail or win4gpg.

When I encode attachments, it gives them a .gpg suffix.  My colleagues
who are using PGP Desktop cannot decode those files.  Though I can
decode their files, either using the gpgee contextual menu or
automatically through enigmail.

Practically speaking, is there a solution for this?  My colleagues are
most likely going to want to continue using PGP Desktop.

Theoretically speaking, what is the difference between PGP and GPG?  Is
it just a different management tool handling the same encryption
algorithm or is there some further translation between the two?  Why
does my Enigmail menu on Thunderbird say OpenPGP, but it is using the
GnuGPG engine?

Thank you!