Can’t get emails

Device or computer?

IOS

Have you tried deleting the account(s), restarting the device, and then adding the account(s) back?

Mail – Setup on a device    -

Mail - If you can't receive email on your iPhone, iPad, or iPod touch    *

OS

Troubleshooting Apple Mail

What does Mail/Window/Connection Doctor Show? If the server is red, select it and look at the Show Details box.

Mail: Mail troubleshooting 

Mail: If you can’t receive messages.    

Mail not sending or receiving messages after updating OS X.