I have had this before and it resolved itself so try the following.
Is your email accesible online like gmail or hotmail etc, i would check and see if you can log in using your safari browser. This way we can tell if its your email or the device.
If thats ok try to
Go to your settings app, then go to mail and ensure your settings are correct.
If it still does not work and you are sure its the device then
Close all apps by opening the taskbar (double click home button) once apps are closed then hold the power button and and home button together until the ipad resets and the apple logo appears. You should see it go back to your lockscreen after a minute or two and then try your mail again.
Always beaware you do not click on any suspicious links in emails as some are designed to steal your information login information so be sure to familirize yourself on changing passwords regularly especially if you have sensitive emails.
Hope this helps resolve the issue.
