Deleting an e-mail account from the default Android e-mail app is not possible.
However, you can just disable the notifications for that specific e-mail account so you won’t be bothered with it.
Start the app.
Go to Settings (top right corner), click on the e-mail account that you want to disable, uncheck the box from “Email notifications”.
That is pretty much it. You won’t receive any notifications in the top bar of your tablet/smartphone.
The account will still be on your device but it won’t bother you with anything.