How do you keep sent emails in the PST folder in outlook 2013


Outlook version
Email Account
Exchange Server
I have recently installed Office 2013 and use my own PST file called MartinG.pst. In office 2013 when I send an email it keeps the sent email in the exchange server "sent items" folder. How do I permanently have all sent emails stored in my PST "sent items" folder. I know how to do it on an individual basis (per email) but I do not want keep setting this every time I send a new email.