Missing 'Summarize Message Previews' option in Mail app on iPhone 17 Pro Max

I’m using an iPhone 17 Pro Max with iOS 26.1 and the Mail app to read all my formal emails. Earlier, when I opened Mail and switched my phone to landscape mode, the reading panel used to appear full screen automatically.

However, on my new 17 Pro Max, the screen now shows the mailbox on one side and the reading panel on only half the screen, which is not user-friendly. When I checked further, I noticed the “Summarize Message Previews” option is missing from the Message List section in the Mail app settings.

[Re-Titled by Moderator]

Original Title: on my new 17 Pro Max, the screen now shows the mailbox on one side and the reading panel on only half the screen, which is not user-friendly. When I checked further, I noticed the “Summarize Message Previews” option is missing from the Message List s