Endpoint Encryption

Is there any way to somehow retain the original unprocessed message as it was receved by PGP Desktop email proxy? Ideally I would like the unprocessed message to appear as an attachment.

Why do I need this? Because in future I may need to prove that that partucular message indeed had a digital signature of my correspondent. Right now, I am left with "PGP Signed" annotation, which amounts to, well, nothing.

Any advice is appreciated.

I believe you can do this with an Exchange Server using MAPI.

I don't think this is what you want, but you can have all PGP/MIME email delivered without use of the email proxy, by having separate PGP messaging services for the outgoing email and incoming email, and disable the incoming service.