I have always had all sound schemas set to no audible alert for an incoming email. So when Outlook all of a sudden started (very loudly) beeping at me every time I received an email, I was going nuts. Not to mention I almost hit the ceiling if one came at a time of deep concentration. (I do not know the cause, but it starting happening just after Windows downloaded a flurry of updates.)
Thankfully, one of my tweeps knew the solution: Start run –> net stop beep
It worked!! I am once again receiving my emails in blessed silence.