Scanning encrypted Mails

Hi folk, I look for a solution to encrypt/decrypt mails. But, I have to scan them for malicous code also. All suggestions are welcome. I would prefer a centralized solution (8 Branches 500 Mails per day) I thought about a second DMZ to encrypt/decrypt on something like a keyserver. Then forward to the Contentscanner and then if the mails are clean forward to the internal Mailserver. Anybody out there know about a "keyserver"? thanks Peter