Outlook Identity - Mac

I am looking for some help regarding my Outlook identity taking up too much space on my mac. Summary:

• Running OS X El Capitan
• 500 GB HD
• Business email is hosted through Gmail
• Use Outlook on Mac for email
• Outlook identity is taking up around 200GB
• HD is at capacity
• Trying to understand the need for Outlook identity. Perhaps for indexing?
• I save every email

Trying to see how I can clean up space as my Outlook identity is using almost 50% of my HD space.

Any tips or suggestions would be much appreciated. Thanks!