Remove Custom Nav Bar on Email Sheet

Remove Custom Nav Bar on Email Sheet

I have this code in my App Delegate:
[[UINavigationBar appearance] setBackgroundImage:[UIImage imageNamed:@"Nav
Bar.png"] forBarMetrics:UIBarMetricsDefault];
This works great, but I use the MFMailComposeViewController and I want it
to have the default NavigationBar appearance.
How do I do that?