Default Email issue

Hey guys. Been having a few emails here or there get kicked into my junk folder (Exchange account, stock email app). I will get the sound alert and see the message in my notification but when I click on the message it disappears. In the past I thought it was just a glitch but just found those emails in the junk folder today while doing some clean up (in Outlook on my desktop).

That sound familiar to any of you smart guys?