Literally every single other email provider I've used/am using allows you to mark a single email within a thread as "Unread" so you can flag that single email for follow-up. Yahoo even used to have that feature until recently. Now, if I want to make sure I follow-up on an email, I have to mark the ENTIRE conversation as unread, so when I do go to reply to that 1 email I wanted to flag, I have to re-open EVERY SINGLE EMAIL from the thread. Frankly that's one of the stupidest, most senseless, and utterly useless features I've ever heard of.