A few years back when researching this problem I ran across a program that came close to being a perfect solution. It would not work for what I needed but I showed me some possibilities that I would like to follow up on. Unfortunately, I cannot find it now, nor do I remember the name.
I a nutshell it would work like this. Instead of creating subfolders in your inbox to separate categories, you create separate PST files. Each PST has the complete set of main folders: incoming, sent delete etc. I actually created a couple so I know it can be done.
In the company I work for they treat outlook like a giant filing cabinet and no one ever cleans up anything so it is only a matter if time before there is a total mess to be cleaned up. Additionally, due to legal requirements, we have to keep all correspondence for 7 years. This means exporting is an absolute necessity.
The program I found did some partial incoming filing by rules you set up that could keep email that was related to a particular project all files in the incoming of that project. The Sent was another thing but I was working on that as I had time.
My goal was to have the single persons email all setup using multiple PST files, one for each "account" the dealt with. If handled properly, it would only take a small extra effort to keep all of the incoming and outgoing email relating to that account inside the PST made for it. When that job was over, the account records closed, I could simply zip up the PST file and store it. This would not cause a problem with any other PST and would totally solve the problem of the 15GB single PST file which even when exported, the best they can hope for is to get their INCOMING email exported as the SENT is still in a single huge mixed up PST.
While it may sound complicated, once I looked at how this other program handles sorting of incoming mail, it made perfect sense and I even set up a trial run for a week just to see how it would work
However, I am just the "IT Guy" so I don't have all these accounts to worry about and no one one was willing to "experiment"
If there is a product that can be purchased that sets this all up properly, I would love to know the name. I know it can be done manually as I did it. But I have never had much chance to try it in action.
Any ideas or if anyone has ever had to work with a setup like this please let me know