The last Office 2016 build update right about 7/5/17 did something to change the sounds in Outlook, running Windows 10. In my case it changed the delete email sound to clear.wav which is a very annoying and unacceptable sound. I searched the web and tried everything I found and I could not get rid of or change this sound. Only thing that worked was to turn off all Office Sounds for all Office applications by going to Excel/options/advanced/general and uncheck the "Provide feedback with sound" box. Just to note the clear.wav sound is the default sound when clearing a cell in Excel.
To prove my point I restored my complete C drive using Acronis True Image to one saved before the update. The annoying clear.wav sound was gone. I went to Outlook and manually updated to the latest Build of Office 2016. The clear.wav sound came back. I restored my complete hard drive a second time and immediately went into Outlook 2016 and turned off automatic updates. It's been fine since.
I am running:
Microsoft Office Home and Business 2016
Version 1705 (Build 8201.2102 Click to Run)
Windows 10 Pro
OS Build 15063.483
Something in the latest Office 2016 build update changed the office sounds. Turning off automatic updates and/or all sounds is not a solution.