How can I encrypt with a PGP pub key

[Robert J. Hansen]

张靖 wrote:
> Is that impossible to encrypt with a PGP public key?

Yes.

> My PGP is FW 6.5.8, and I tested to import the public key to GPG,

6.5.8 is old.  "Decrepit" might be a better word to use for it.  It
_way_ predates RFC4880, and thus you need to tell GnuPG to work around
PGP 6.5.8's limitations.

Add "--pgp6" to the beginning of your GnuPG command line.  E.g.:

gpg --pgp6 --recipient <name> --encrypt <file>