Various and sundry Mac utilities and Mail app add ons also display how many messages are awaiting your already overtired eyeballs. Here’s one that works in the Mac’s Dashboard as a Widget and it’s free.
Look! Mail! No Click!
MailWidget for the Mac’s Dashboard is little more than a simple way to view what’s already in the Mail Dock icon when Mail is running.
The benefit to using MailWidget is that it checks your email accounts in the background, even when Mail is not running.
MailWidget hands basic IMAP, POP, and Exchange accounts, including SSL, but other options are limited. Severely limited. MailWidget is a Widget, not a replacement for Mail.
All you’re getting for free is an easier and faster way to view the number of messages in each account’s inbox without opening Mail. You control the periodic check time length and MailWidget can handle multiple accounts.
There’s a built-in vocal announcement, too, but what I like most is the simple flick of the wrist or swipe to open OS X’s Dashboard app to reveal MailWidget. No clicking. To view the entire email message you’ll still need to use Mail.
The audio feedback notices arrive even without checking Dashboard. MailWidget also supports Growl notifications (but you have to use Growl, not the Widget). It’s not Mail, but it doesn’t have to be. It’s free and yet another way to know about incoming email messages even before they get to Mail.