Do you use Gmail in Chrome? If so then you’ll be able to experience the new update that the Gmail team just rolled out. Because of the technicality of the feature, don’t expect to see it in Firefox soon, and probably never in IE.
A few days ago (6/10) the Gmail team pushed an update that allows users to completely close down the main Gmail window without losing pop-outs. Currently the feature only works if you are using the Chrome browser. Another thing is that the Gmail chat windows still close if you exit Gmail so we’re waiting on pop-out support for that, but emails and everything else seem to work as intended.
Overall it’s nice little update for Gmail and one more, yet small, reason to use Chrome with it.