How to Turn Off iMessage Read Receipts Per Person in iOS 10
With iOS 9.3.5, as well as all of the versions prior to that, you had two choices when it came to message read receipts—either on for everybody or off for everybody. So if you weren't comfortable with one or two of your contacts knowing whether or not you've read their messages, you had to keep the feature disabled and miss out on read receipts for people you're a bit closer to.
This has all changed with iOS 10, and now, you can pick and choose which contacts have read receipts enabled. It's a really simple process, so let's get started.
First, open any conversation thread in the Messages app. From here, tap the "i" button near the top-right corner, then you'll see a new option labeled Send Read Receipts. If you want this person to know when you've read their messages, simply enable this switch. Otherwise, make sure the switch is turned off, and they won't be able to tell when you've read their messages.
This option is only available in iMessage-enabled conversations, but that's to be expected. Regular SMS conversations (the ones with green bubbles) do not support the read receipt functionality to begin with, so the other party will never know if you've read their messages or not. Group messages also don't have read receipt functionality, no matter if they're SMS or iMessages, so keep that in mind.