I'm not sure if the full download of El Capital will move to the desktop once you have downloaded it again or if not, it might stay in the Applications folder. If you want to see the progress of the upload, go to the "Purchased" icon in the AppStore and it will show how much longer it will take to download. If you want to keep a copy of the download, you will have to make a duplicate of it from the one in the Applications folder because once you do the install, it will automatically erase itself.
Based on previous posts (and please don't shoot the messenger, I am only reporting on what happened after I tried some of the stuff I saw posted here), I created a new user and opened a new email account with my ISP provider. Mail sounds were the same I have now, so that didn't work. Tried using the email address as a guest, and the same result. So, according to the following post, my problem is with my base files:
dianeoforegonOct 22, 2015 1:04 PM Re: no mail sounds after installing El Capitan
Re: no mail sounds after installing El Capitanin response to J. Hopmann
The problem has been fixed in OS X 10.11.1 for most users. This suggests the problem is in your User's Library.
Testing in a new User will quickly tell you if the problem is system wide or if it's your User's folder that contains the problem.
You can use the Guest User or create a new User for testing.
Add one of your email accounts and test.
CREATE A NEW USER
Go to System Preferences --> Create a New User in Users & Groups.
Switch to the New User by logging out/in or use Fast User Switching
Do you still see the issue?
If yes, then the problem is with your base files.
If no, then the problem is in your User's folder.
dianeoforegonOct 22, 2015 1:32 PM Re: no mail sounds after installing El Capitan
Re: no mail sounds after installing El Capitanin response to Peter Savage
If it's base files, I would download the El Capitan installer again and run this over my current install.
If it's your User's folder, we can try resetting your Mail files.
So, following this advise, I'm downloading the full El Capital installer again and will run it again over my current install to see if this fixes the issue. If that doesn't work, I will simply give up because I'm tired of trying all this c**p (pardon my language)