HTC One M7 :: Categorizing Emails As Favorites

I had previously posted this question in the "Kitkat" forum, however didn't receive any response. I was later told that The email client is an HTC Sense creature, not Android. I'm carrying an HTC One running Kitkat. I note that the stock email client has a "Favorites" window if I swipe left. Currently, I have only one email in that area, though I don't know how I got it there. More importantly, I don't know how to get others there. There doesn't seem to be an option to mark the email as a "favorite", nor anything else that would be obvious.

I did notice that within Outlook (on my desktop) I can categorize emails as "HTC Favorite"; I tried that with a couple of test emails, but that doesn't seem to have moved the emails over to that "tab". I don't know how the "HTC Favorites" category came into being, but I assume it occurred once I started using the One with my existing Outlook. I also note that Jerry ran an "Android 101" some time back about favoriting contacts.

As a coincidence, the one email I have in "Favourites" is from my wife, who I note is also categorized in my Outlook as an "HTC Favourite". How my phone, Android, or Outlook new to categoize my wife as a favourite, I don't know. A bit presumptuous, perhaps, but it works. Could it be that because she is a "favourite" contact, that her emails are automatically "favourited"? Is there another way to move emails over to "favourites", particularly without favouriting the contact?

I've now figured out that the contacts marked "HTC Favourites" happen to be those contacts for whom I created a speed dial entry...so that mystery is solved.