Mail program stop working on original iPad

Got no warning sign. Apple mail program suddenly stop working. Can not send or receive new mail. The various mail boxes do not show on the screen anymore (new incoming, sent, trash, they are all gone). Checked all the mail settings are correct, WIFI working fine. How do we reload Apple Mail program without having to reconfigure everything else?

When I turn on the mail program, the display show a blank Mail layout than the screen switch briefly to black and the mail program shuts down.