I moved ALL the emails from my A.pst to A1.pst and A2.pst.
Originally, my A.pst was about 8 GB, A1.pst became 4 GB, A2.pst became 3 GB but after the move, A.pst is still 3 GB. Why is this Pst not smaller?
You need to Compact it after moving the email. Go to "Data file properties", click the "Advanced button..." and then click "Compact Now".
Right click the PST in outlook and go "Data file properties..." then select "folder size..."
This will give you a break down of where and how much data is stored in your PST