My iphone 5 shows 2.8 gigs of email on my phone that isn't there

My iphone 5 shows 2.8 gigs of email on my phone, but there is only about 500 kb actually on the phone. I'm trying to free up space on my phone but after removing all but 5 small emails from my phone it still shows I have 2.8 gigs of email on the phone when I go to manage data. I've emptied all the trash cans, drafts, sent emails from my phone and rebooted the phone but the results are the same. Where is it reading the emails from and how do I free up the space?