Mail will not make a sound when sending mail

[Hustle]

I got a Alu Macbook last week and since I've had it, it will not make a sound when receiving emails, only show as 1 email in the dashboard.

I've checked the settings, changes the sound, created a new user account.

I've just phoned AppleCare and they have no idea and have told me they're going to ring me back in a few minutes.

I'm baffled. I've had macbooks before and none of them have ever done this.

Has anyone got the same problem?