528,000 People Are Still Waiting In Line For Mailbox, The 37-Day-Old App Dropbox Just Acquired

File storing and sharing company Dropbox has acquired Mailbox for an undisclosed amount.

Mailbox is an app that promised to help people reach Inbox 0 with easy archiving and save-for-later features.

What's crazy is the app only launched 37 days ago, on February 7. And, thanks to a brilliant marketing scheme that makes people wait in a virtual line to access the app, there are still 525,000 who are patiently waiting to try it out. CEO Gentry Underwood tells The Wall Street Journal that 1.3 million app reservations have been made and 60 million messages are being delivered daily over the service.

"We are still struggling to keep up with the demand from those who want to use it,” he told WSJ.

While the price wasn't disclosed, it's safe to assume Underwood and his 13-person team jumped ship for many millions (and hopefully a ton of stock options). They had raised $5.3 million to date.

Dropbox may have pounced too early though. Many who tried the app have already stopped using it. When companies buy into fads, it doesn't often work well. Zynga, for example, purchased OMGPOP while its app Draw Something was exploding with traffic. Almost as soon as Zynga paid ~ $200 million, Draw Something's traffic declined.

Here's what the Mailbox waitlist looks like now. Dropbox plans to keep the app running separately from its main app, so everyone should be able to get access to Mailbox despite the acquisition.