I built a write only email archiving system on top of our in-house Exchange system so my organisation could meet it's email retention and data protection respon

I built a write only email archiving system on top of our in-house Exchange system so my organisation could meet it's email retention and data protection responsibilities. It's a shared mail store where people can create folders, add retention periods to those folders, and share them with other people. Once you drag email into those mail folders, they can't be removed other than by reaching their retention period limit. We purposefully keep their "live" mail quota low to force people to properly archive their email. GMail is fine for basic email use. That's it. You want to do anything remotely interesting, you need to do it in-house.