Any app/utility to modify mail in quarantine transparently?

Do you know of an application or a utilty that can modify a quarantined email message without leaving any fingerprints?

The business managers want to inspect and if necessary, correct the emails of their new representatives without being detectable. The recipient would only see that this came from the original sender. Also, any replies would go right back to the original sender.

I’ve found an email filter which sits on a seperate server in front of the Exchange 5.5 server. This application supports a quarantine where messages can be reviewed by managers and released without leaving fingerprints.

However, they would like to be able to make corrections to certain messages, and do so without leaving a fingerprint.

Any ideas?