As most of you that downloaded Windows 8.1 RTM may have discovered by now, the built-in Mail app has gone from “Good-enough” to “Awesome!”. Yes the mail app has truly grown-up. It can now compete with any mail apps out there, maybe even surpass some of them. But with this awesomeness comes some pitfalls.

Microsoft has added Folder views to the left side of the App (indicated). By default, this folder view contains the Inbox Icon at the very top, and a few “virtual folders” thereunder for Favorites, Flagged, Newsletters and  and Social Mails in order. Then you have the real folder list Icon at the very bottom. The intention of the Folder-view feature is to let you glance your mail app and see what has changed by adding number to the right of those Icons corresponding to number of mails that has arrived in those folders since you last checked.

It all works fine till you discovered you’ve defined some important folders on Outlook.com site to automatically sort your mails to those folders. For example, for me, I have defined a personal folder called “Shopping” to automatically receive mails from eBay and Amazon etc. So like I said, everything works well in the new Mail app, you take a look at those left side icons you don’t see any numbers next to them, you assume all is OK, till you open the bottom-most Icon and realize you’ve got mails in your personals folders that you would have missed if you went away after seeing nothing on those topmost folders.

So to see latest mail numbers on your custom folders, you need to add them to your favorite folders by clicking on the bottom-most icon and clicking the favorite (Star) icon next to them. Once you do this, Mail MX adds those folders under the Custom Folders icon as below:

So, if you’ve got that important custom folders defined with rules, you want to add them to favorites to be able to see their updates. Now you know.