Compress your Outlook PST file by using "Compact Now" feature of Microsoft
Outlook. But, the size of your PST file is quite large so please don't take any
risk with your important Outlook data files. I mean to say that you should go
with any third party software. I would like to give you two better solution on
the behalf of my personal experience. First is obviously Compress your PST file
and the second one is PST Compact and Compress Tool.
Learn more info at :-
http://migrateemails.com/2016/09/14/compress-pst-compact-pst/