Access your settings
Scroll until you find "Mail"
Click into accounts
Select the email you are having troubles with. Once you've selected make sure the toggle option is on for that email.
Additionally sometimes you won't receive emails is because you need to update your password for the email account.
Access the email account you are having issues with also make sure the toggle button is on to access emails.
In other forms of making sure your email is functioning. Please ensure that you have network access. Wether it might be your carrier network or your Wifi ensure that you are connected properly.Â
If you are on cellular data, open the Settings app > Cellular > scroll down and ensure the switch next to Mail is green.
Closing out all of your apps and reopening and fix the issue. Restarting of your device is helpful as well.