How to Prevent Mail on Your iPhone from Organizing Messages by Thread
In your iPhone’s Mail app, your messages get grouped by thread, which means the original message and all the replies you’ve received are grouped together in the account’s Inbox folder. This is usually remarkably handy, because it means you don’t have to scroll through a million messages to locate the reply you want to read.
Mail indicates a thread by displaying a double arrow (>>) instead of a single arrow (>) to the right of the first message in the thread. Tap the message to see a list of the messages in the thread, and then tap the message you want to read.
Organizing messages by thread is usually convenient, but not always. For example, sometimes you view your messages and scroll through them by tapping the Next (downward-pointing arrow) and Previous (upward-pointing arrow) buttons. When you come to a thread, Mail jumps into the thread and you then scroll through each message in the thread, which can be a real hassle if the thread contains a large number of replies.
If you find that threads are more hassle than they’re worth, you can follow these steps to configure Mail to no longer organize messages by thread:
On the Home screen, tap Settings.
Your iPhone opens the Settings app.
Tap Mail, Contacts, Calendars.
You see the Mail, Contacts, Calendars settings screen.
Tap the Organize By Thread switch to Off.
Your iPhone saves the setting and no longer organizes your messages by thread.