iOS 10 has been available for over six weeks, and during that time I’ve had lots of attorneys ask me questions about the changes. By far, the #1 question that I have received has been along the lines of “how do I fix my email after upgrading.” And I just received that question again yesterday, so I know that folks continue to be annoyed.
After asking what they mean, everyone seems to be discussing the same pattern, the way that iOS 10 can group your emails together. If you receive multiple emails on a subject, such as a group email to more than one person in which there are multiple responses, the Mail app in iOS 10 can group all of those messages into a single thread. Tap on that single thread to see all of the associated messages.
You can tell that threading is being applied to a message because you will see >> — two blue chevrons — at the far right next to a message thread.

If you tap on the message, you will then see a bunch of individual messages, each separated by a thin gray bar.

I can understand how this view might be appealing to some, but I don’t like it. I’d rather see each of my email messages on its own, appearing in my list of emails by date, and not grouped together in any way. If threaded emails also annoy you, you can turn threading off by going to the Settings app on your iPhone and then selecting Mail.

On the next screen, scroll down until you see the Threading options. Turn off the first one called “Organize by Thread.” I actually have all three of the Threading options turned off, but just turning off the first one should be enough for you.

Hopefully, these steps will return your Mail app to the way that you think it is supposed to be working.
The main issue is that Apple did threading poorly. Third party apps like Spark did it correctly, mimicking the behavior of Gmail on the web, where you can expand and contract previous messages to make it less of a scrolling nightmare.
With threading off the email experience is rather poor, as it was before, as you cannot see the prior messages exchanged (without more scrolling in the quoted text) to see the context of the discussion. This is especially important when dealing with settlement and seeing what your prior offer was and what was discussed before responding.
THANK YOU THANK YOU THANK YOU!!!!!! This is an exaggeration, possibly, but you’ve changed my (email) life! 🙂
Thank you so much for explaining the whole process in detail. This is so helpful for me.