I am not able to see my emails on my iphone, why?

Have you tried deleting the account, restarting the device, and then adding the account back?

Mail – Setup on a device    

Mail - If you can't receive email on your iPhone, iPad, or iPod touch     

Did you happen to either get a new phone and did not back up your old one and redone it form backup to check the mail accounts you have on your iPhone go to settings > Mail > Accounts.