Please try the following:
Please perform clear cache of email app folder and check if it works.
Go to Settings> Apps> Select the emaill app> Storage> Clear cache.
Then reboot your device once.
Please try to contact the service provider as the issue might be from their side.
Please perform the wipe cache partition of the device and check if it works.
If the device is not working correctly, you may need to master reset it and also clear the cache partition. These two resets clear different parts of the device storage. Unlike a master reset, wiping the cache partition does not delete your personal data.
1. Turn off the device.
2. Press and hold the Volume Up key and the Bixby key, then press and hold the Power key.
3. When the Android logo displays, release all three keys.
4. An 'Installing system update' message will show for 30 - 60 seconds before the Android system recovery menu options appear.
5. Press the Volume down key several times to highlight wipe cache partition.
6. Press the Power key to select.
7. Press the Volume down key to highlight yes, them and press the Power key to select.
8. When the wipe cache partition is complete, Reboot system now is highlighted.
9. Press the Power key to restart the device.