Q: Sound Effects Not working Correctly in Mail 6.0 or Notification Center...

Bloody annoying.

Lost my email notification sounds and dont seem to be able to get them  back!

I have the same issue with sound notification on my new macbook air 10.8.2 and the mail and notification center.  I find that closing and then re-starting mail fixes the issue temporarily.  Need a fix from Apple!!

seems like a fairly widespread problem! hopefully Apple may help us faithful Macusers out

I've been having this issue for a year or so, on both a last gen MacBook Pro running 10.7 and and a new Retina model running 10.8 with all fresh installs.  I came across a blog that said plugging headphones into the jack will fix it and indeed it does (it takes two tries sometimes).  However, like the coreaudiod temporary work around, the issue comes back.  I'm pretty sure it happens after the system awakes from sleep. 

This has been an issue for long time.  I'm surprised it's still unresolved.

your post and a few others pretty well rules out any theory that it's caused by any other application 'foreign' to M.Lion.

yes indeed, very surprising - and often quite frustrating. with all due respects, one would think, at least hope, that it will be easy to solve when given the appropriate time and attention by the experts

Just bought my RMBP 1 week ago.  I believe it came with ML 10.8.2.  I also don't hear any email notifications.  I bought this new machine for my ecommerce site only to find out I can't hear my Orders coming in.  Can't run a business efficiently if I can't hear my emails. APPLE PLEASE FIX ASAP!.  I didn't invest $2500 to make my business inefficient.  My old 7 year old macbook to say the least is more reliable when it comes to emails.  Sadly, I am currently relying on my Iphone4s to notify me of incoming emails while my computer is sleeping.  Tim Cook(slim shady) selling bad apples.  Miss the real slim shady!

I had same problem and after a little research I think I found the issue on my system. Run the Audio MIDI Setup application (in Utilities). In the left pane you will see a list of Audio Devices. Make sure the Built-In Output has the icons shown. If not, select the settings button at the bottom of the left pane and select "Play alerts and sound effects through this device." As soon as I changed this, things started working correctly. Hope this helps someone.

Thanks.

Interesting; I had not gone to this app before. Unfortunately, when I click on the settings button, the option to "Play alerts and sound effects through this device" is greyed out (see screenshot). 

Note that the combination of quitting the "coreaudiod" process and restarting Mail is still enabling sound effects to come back temporarily for me.

Did you experience the delay in audio like the other posters here or did you simply have audio that was not working? In any case, this is not much use for people who don't want to use the built-in speakers, on a Mac Pro those sound awful.

My "Play alerts and sound effects through this device" is also greyed out.  My screen shot looks exactly like Jensen's posted here.  I wonder because the sound icon is already present next to Built In Output that it is *already* selected to be used for sound output (which is which the dropdown menu seems to be explaining...whichever the device the sound icon is present for, that's what it will use).  So we are selected correctly, already.

Now, I *have* been using Audio MIDI for the workaround posted on this stream..to use the drop down menu on the right hand side from -24bit Integer to something else (and then listen to all the queued up sounds get played) and then back to -24bit...which lets it work correctly for awhile before it stops (probably after a sleep, but not always).  Sometimes this does NOT work (no queued up sounds...but also, no sound coming from actions).  And then I just sigh and give up...

Yes, it's supposed to look like that, it's greyed out because it's already selected. The setting only makes sense if you have multiple audio devices.

Mine's working fine now, I got the impression Apple had Fixed it.

But I am switching the computer off relatively frequently which  might be refreshing it Enabling the sound to work properly. Good luck everyone I'm calling this fixed.

I agree with your latter assessment. It's just the turning on and off of the machine that's making the sounds actually work again. I think what it does each time you turn the machine completely off is to reset all the audio functions.

Anyway take my word for it, it's definitely not fixed…

ummm....I never reset my iphone and the sounds/notifications always work.  I don't like the idea of turning my MBP Retina on and off just so I can get sound working. 

Problem fixed. Thanks