Do you have the same type of email accounts? That's all I can think of off the top of my head.
Also, try a few more test emails if you can. It might be a fluke. Happens, after all they are computers.
A restart is worth a try. Hold down the power button until the red power off slider appears, then side off. After the iPad finishes shutting down hold down the power button until the Apple logo appears.
Sometimes this fixes the strangest things, and sometimes not. In this case probably not, but worth a try just to eliminate the obvious.