@javajiver: If you're using the Samsung Email app then please ensure you are connected to Wi-Fi or Mobile Data, then open your Email app > Tap the 3 lines in the top left > Tap the cog in the top right of the pop-up box > Select your email account > Sync Account > On > Swipe from the top of the screen to the bottom > Select 'Sync' from the Quick Panel. While you are in the Email Settings menu please check your Sync Schedule and Sync Period, and make sure you have Limit Retrieval Size set to 'No Limit'. If the issue persists, please try removing the account and re-adding it via the steps below to see if this helps.
Settings > Accounts and Backup > Manage Accounts > Email > Remove Account > Manage Accounts > Add Account > Email, and fill in the required fields.
Alternatively, uninstall and reinstall the Email app, as this has also been known to address any temporary sync issues.