No new mail notification sound.

Hi there,

I have just switched from Windows and purchased a brand new 27" iMac. I'm running OS X 10.6.4 and have one issue that I can't seem to resolve.

When new mail arrives, the notification sound doesn't play. I have the 'New Message Sound' set and all other sounds work perfectly (such as the sent mail sound).

I'm sure this is probably user error, but it's driving me crazy and could use some help!

Thanks in advance,

Martin