Is there an easy way to tell what specific public key was used to encrypt an email?
My email gateway isn't able to decrypt an inbound S/MIME message and I'm suspecting that the remote sender may have used an obsolete public key that is no longer in use and doesn't match my private key.
Is there an easy way I can tell if the public key the sender used matches the private key I have?
Likewise, is there a way to do this for PGP encrypted emails?
Ideally I'm looking for something I can check with via the Linux command-line or native Windows tools without needing to be at either users desktop or loading all the keys into my desktop (in case this happens for multiple users).