[Exim] server-side management of public keys?

Where I work, we're evaluating a very nice product for MS Exchange that
takes a lot of the configuration and headaches out of managing public
keys. With this system, you install someone's public key into the keyring
once. Then, when anyone submits an outgoing message to the Exchange
server, it checks to see if it has a public key for that recipient. If it
does, it automatically encrypts the message with it and sends it on its
merry way. Incoming messages that are signed are automatically verified,
assuming the server has that sender's public key on file.

The best thing about this is the clients require *no* special
configuration to use this system. It's managed entirely on the server
side. This means that I can connect to my email via the Outlook client, a
Blackberry or via our webmail interface and not have to worry about public
keyrings in either place.

Anyone know of a similar solution for a Exim?

Thanks.

--kurt