So you were unable to set up message filters like:
if body begins with -----BEGIN PGP MESSAGE----- and ends with -----END PGP MESSAGE----- - keep on server or forward to
blah@blah.comif body doesn't begin with -----BEGIN PGP MESSAGE----- and ends with -----END PGP MESSAGE----- - bounce with message sorry blah blah blah, then delete from server
?
What I tried to do was have a "pipe" filter in exim that would call gpg on the body to check if it is a pgp encrypted message to my public key. I could never get a pipe filter to work at all.
I never tried to make a simpler filter to check if the beginning/end of the message has the form you suggest. I don't know how to do that either, but I have a strong feeling if I did most of my emails would look like
-----BEGIN PGP MESSAGE-----
Unencrypted content
-----END PGP MESSAGE-----
Out of curiousity though, how would you implement the kind of filter you're suggesting?