I tend to use my mobile phone for most things, even receiving and sending emails, I decided to use my tablet yesterday, and noticed how many emails I had never received to my phone, but which were on the tablet, it's the same email address, why would this happen.
Perhaps there is not enough memeory in your phone to accept more, or the settings have been changed.
Try going into phone settings, accounts, sync accounts and see if it updates the emails on your phone