The company announced the change on its official blog, opening up the doors and ditching a waiting list of hundreds of thousands of people. The change was made after 10 weeks of behind-the-scenes effort to scale the service.
Mailbox revealed its service is now delivering more than 100 million messages per day, and the company is confident it will be able to handle an influx of new users. The application is a free download available on the iPhone App Store.
The first-come, first serve reservation system disappeared just a day after a the software was update to version 1.2, with enhanced features such as smarter snooze settings and swipe gestures.
Since its debut, Mailbox has filled over 1 million reservations. The Gmail-driven service was acquired by cloud storage giant Dropbox in March for between $50 million and $100 million.