I just purchased an iPhone 13. All of a sudden, my email only opens in landscape mode. The orientation button is off. All other apps work just fine. Any ideas?

You are right. Most of the time the simple action works. Below is another simple action that you can use if the iPhone OFF and then back ON method does not work:

Try and Force Restart your iPhone EXACTLY as shown below and see whether that resolves the issue:

• Press and quickly release Volume UP button
• Press and quickly release Volume DOWN button
• Press and Hold the SIDE button until an Apple logo appears and then release the Side button (Can take up to 20 seconds. (DO NOT release Side Button when invited to Slide Power OFF). 

Axel F.