Monitoring outgoing email (revisited) -- bcc send

There has been a similar thread in the past - Monitor Outgoing Email

But this isn’t quite the same.

What I am trying to do is capture all email sent through a specific user account in order to back it up.

My final goal is to have a real time backup of my email on an independant sever (such as a gmail account). Incomming email is simple enough, but outgoing posses a problem.

I always use IMAP or webmail, so I could resort to a complicated crontab solution, but that wouldn’t be real time.

What I envision is a server-side filter that forces all emails to be BCCed to a third email address, adding a custom header so I can filter them out as “sent” mail on the other end. (think procmail for outgoing mail)

–Note the potentail abuse\legality concerns of this feature is more or less the same as the previos thread. No need to duplicate that conversation here.