Mail read-confirmation on Mail.app in Mac

This is very useful and hidden feature of Mac OS X.

From now on, don't be concerned about whether your mail is read by recipient or not.

With very simple setting on Mail.app, you can receive mail confirmation.

First, quit your Mail.app if it is running.

Then open "Terminal".

Type below commands in Terminal.

defaults write com.apple.mail UserHeaders '{"Disposition-Notification-To"="your@address";}'


Replace "your@address" to your real email address.
That's all!!
Unfortunately, Gmail doesn't support mail confirmation service.
So you may call recipient whether he (or she) got your mail if you are about to send email to gmail. lol