Gmail with Background Send

There's a new Gmail Labs feature that will certainly appeal to anyone sending countless emails in Gmail every day: the Background Send.

Although Gmail is quite fast, we all know just how valuable time is, and every second counts. When you enable this Labs feature, your Gmail won't delay you whenever you send an email. Your Gmail will be immediately ready to do whatever you want, while your email is being sent in the background.

If anything goes wrong, you'll receive an alert notification:

The only thing you'll have to keep in mind is to make sure every email was sent before you close your Gmail window or shutdown your computer.
I think it's a reasonable compromise in order to shave all those precious seconds every time your hit the send button.