user email sent with administrator account

I have a brand new install of an exchange server 2013 with 2 email accounts on it, administrator@example.com and pete@example.com.  When I send an email with the account pete@example.com, it sends it out just fine but the recipient sees it as being sent from administrator@example.com.  

I am new to exchange and am fairly clueless about it.  

I have looked in all the obvious places, but honestly, I am not even sure what the obvious places are.  

Any help or clues would be very appreciated. 

Thank you