Make MacBook Pro announce emails when sleeping I'd like to make my MacBook make a sound when I receive a new email, even when it is sleeping.

Is there any way to do that?
No - sleep precludes the making of sounds. 

You can set the Mac to prevent sleep and instead just put the screen to sleep but anything that runs on the CPU will need to machine to exit from sleep anytime a mail arrives in order to produce the sound you wish to be made.