Gotta love Outlook compacting

I've already done a bit on the most efficient way of reducing the size of Outlook files looking at how insane the compaction method is, but let me bring that home with some real figures.

I've a main PST file and an archive PST file. I need to do some archiving so I compact them both. They are both fully compact and can be shrunk no further. I now transfer some of the data from one to the other and the archive PST file increases by 180Mb. What do you think would happen if I tried to compact the archive file?

If you answered nothing as I've obviously just transferred some fully compacted data you obviously don't work for Microsoft. The answer is I remove another 70Mb of data. So only 100Mb was actually there? What was the other 80Mb that was supposedly already compacted? Who knows. So what happens if I compact my original file from which I removed 180Mb of (supposedly) compacted data?

It decreases my 160Mb.

So removing 180Mb of data allows me to reduce my file size by 160Mb, but there was only really 100Mb worth of information there.

Brilliant.