For #3 from the support docs on Apple.com, you don't need to restart your iPad -- you need only restart the Mail app. Exit from the Mail app by click on the home button to take you back to the main screen of your iPad. Double click the home-button to display the status bar and press on the...
This is when both orientation button/settings doesn't resolve the situation. Orientation settings is not locked by the mail will still not respond to current orientation of the iPad. I found that if you kill the Mail app and restart the app, the mail app will automatically adjust to your iPad...
Greetings, new here and I was looking for solutions to permanently fix the iPad mail orientation being stuck issue. I posted my quick fix but still looking for an actual fix.