Thanks to user Hotel Bravo who found this workaround. I've found a solution! Well, sort of -- it's a workaround, but it solves the issue.        
Hi there, Since I have installed DDM (Dell Display Manager), I have noticed that my shortcuts in MS Office (Outlook and Excel) stopped working. E.g. Alt + S to send an email in Outlook. Once I quit DDM, my shortcuts start working again. I am wondering how to have DDM running while not interfering with MS Office shortcuts? Thanks lukas
U3223QE, DDM 2.0, taking Alt + S shortcut