This isn't just an Apple Mail thing... I recall it happening other times as well, such as when SOMETHING completes, whether a file copying, or whatever. When I send an attachment through Mail, and the email completes sending, my iMac makes a very loud BRRZZT noise. It's not any of the alert sounds in the Sound Preferences Pane, and turning down the Alert Volume in System Preferences doesn't stop it. It sounds like feedback from the speakers... like the warbling buzz you hear when you touch your finger to some powered speakers' headphone jack and the subwoofer crackles and the speakers buzz. Except, it's very loud, and catches me totally off guard. Even while I'm listening to music, I may leave the email to send on its own, and while typing in MSN, or browsing the web, ill hear a sudden loud BAAZRRT and i'm caught totally off guard. It's rather annoying. Could there be something wrong with my speakers? Or what? Is it a software or a hardware problem? =\ Any ideas?