I had a fairly large zdb file (about 7GB). Cleaned out a lot of stuff into pst files.
Then compacted. This got the zdb file down to 5GB, not great, so *lots* more cleaning out.

Now I have Outlook reporting a total folder size of about 300MB.
But compacting does not reduce the zdb file below 5GB and it returns suspiciously quickly.

What can I do to get the 5GB down to something that is similar to the 300MB that is actually being used?