I don't have a Win10 machine here to look at but I recall some control of sound in Settings > Notifications & actions but don't recall whether this controls notification sounds only or whether the delete sound is considered "notification" sound. 

I checked my Win7 machine and find the delete sound to be the system sound associated with an Exclamation event.  You should be able to confirm whether it's the same on your machine and have the option of assigning a different sound file.  I don't know of a way to turn it off from within Pegasus Mail.

Good afternoon all.

Having just had to re-install Windows 10 after a catastrophic update failure emptied my PC, I now have an annoying sound whenever I delete a message. I cannot find anything in the Help System that explians how to kill that sound. I think it may be the fault of the default Windows Sounds settings, but I cannot see a sound for "Delete mail message", nor for "Delete anything at all". So does anyone know which Windows Sound sertting is causing me as much annoyance as music in a quiet pub?

 Thanks indeed

Kenneth Spencer