Assuming your using Samsung Email App - in the app go to Settings - ( tap the 3 lines at top left then tap the cog at top right of next screen that comes up ) Tap on the account you want to change then tap " Email Sync schedule " then tap " Set sync schedule" and you will see various options eg auto for constant updating as Email received, every hour etc etc
If you have more than one email account you need to set the schedule you want for each one