Do you have to stay in classic view?
I tried this and now I get a sound but no banner. Turned classic view off and now I get neither a sound or a banner.
After you get the sound, can change back to new view !!!
I also got no sound later on after I tried this method for the 1st time but try to do the trick again and there you go. Also remember to check the New Messages Sound in Preference/Generals, try to pick different sounds as well
_ Preference/Viewing/Classic View on. Quit the app, open again, ask a friend to send u an email. Turn off classic view.
For the banner to appear there are 2 conditions that must be met
1. The mail must come from an account which is not in your Mail app
2. When you are selecting another window or app
At this moment I'm trying to send me some emails from friend accounts to different accounts of mine in Mail app and I still get banner and sound.