Not sure if this question belongs in the HTC area, or if it's more of a general Android question. I'm carrying an HTC One running Kitkat. I note that the stock email client has a "Favourites" 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 "favourite", nor anything else that would be obvious. I've searched around, and noticed that someone asked this very same question on another Android forum, however it doesn't look like they ever got an answer.
I did notice that within Outlook (on my desktop) I can categorize emails as "HTC Favourite"; 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 Favourites" 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 favouriting 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?
Edit: 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.