1000 apologies for opening an old thread, but this would be quite easy to do. I write a lot of Database programs commercially and this would be quite straight forward to achieve. The *downside* is that as it would need to run as a policy, it may slow down the processing of mail as each one needs storing before the policy task completes. Have to say I don't know if Mercury processes these in parallel or series.
That aside, we can have Mercury pass the email text to an application that then inserts them into the required database.
Drop me a line if you still (after all these years!) think it's worth looking at.